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.. NOTES
See "HOW TO ADD A COMMAND-LINE ARGUMENT" in README-maintainer.
This file contains text that is used for help file generation.
Lines that start with the magic comment ".. help topic x: y"
introduce a help topic called "x" with short text "y". The contents
of the comment are the long text.
The ".. qpdf:option:: option" directive introduces a command-line
option. The next ".. help: short_text" comment's contents are the
long text of the help. Search for ".. help-topic" and "qpdf:option"
for additional help. Command line arguments can be referenced using
:qpdf:ref:`--option`. They also appear in an index.
Note: 2022-01-22: because short help text is used in the "schema"
JSON object for QPDFJob JSON, we can't end short text with a ``)``
character since doing so would cause ``)"`` to appear in the string
literal. We use the R"(...)" syntax for these literals, and that
looks like an end delimiter. While the C++ spec allows
R"anything(...)anything" specifically for this purpose, the MSVC in
CI at the time of this writing did not support that construct.
STYLE NOTES
In this text, :samp:`...` and ``...`` are used somewhat
interchangeably. :samp: should be used when there is replaceable
text enclosed in curly braces. Otherwise, either is fine. Ideally
there should be a stricter editorial convention, but they render
the same, so I have not gone to the trouble of making it
consistent.
USE :qpdf:ref:`--option` to refer to an option whenever it is
specified without parameters in any place other than its own help.
This creates a link.
When referring to command-line options, use the following
terminology:
argument: any command-line argument whether option or positional
option: any argument starting with -- including its parameter, if any
flag: the --flag part of the option; only use to disambiguate
parameter: the parameter part of the option
Example: qpdf in.pdf --object-stream=generalized out.pdf
Each word is an argument.
The "--object-stream=generalized" option consists of
the "--object-stream" flag with the "generalized" parameter. It
would be okay to talk about "the --object-stream option" in the
text if there's no ambiguity.
.. _using:
Running qpdf
============
This chapter describes how to run the qpdf program from the command
line.
.. _invocation:
Basic Invocation
----------------
.. help-topic usage: basic invocation
Read a PDF file, apply transformations or modifications, and write
a new PDF file.
Usage: qpdf [infile] [options] [outfile]
OR qpdf --help[={topic|--option}]
- infile, options, and outfile may be in any order as long as infile
precedes outfile.
- Use --empty in place of an input file for a zero-page, empty input
- Use --replace-input in place of an output file to overwrite the
input file with the output
- outfile may be - to write to stdout; reading from stdin is not supported
- @filename is an argument file; each line is treated as a separate
command-line argument
- @- may be used to read arguments from stdin
- Later options may override earlier options if contradictory
::
Usage: qpdf [infile] [options] [outfile]
The :command:`qpdf` command reads the PDF file :samp:`{infile}`,
applies various transformations or modifications to the file in
memory, and writes the result to :samp:`{outfile}`. When run with no
options, the output file is functionally identical to the input file
but may be structurally reorganized, and orphaned objects are removed
from the file. Many options are available for applying transformations
or modifications to the file.
:samp:`{infile}` can be a regular file, or it can be
:qpdf:ref:`--empty` to start with an empty PDF file. There is no way
to use standard input since the input file has to be seekable.
:samp:`{outfile}` can be a regular file, ``-`` to represent standard
output, or :qpdf:ref:`--replace-input` to indicate that the input file
should be overwritten. The output file does not have to be seekable,
even when generating linearized files. You can also use
:qpdf:ref:`--split-pages` to create separate output files for each
page (or group of pages) instead of a single output file.
Password-protected files may be opened by specifying a password with
:qpdf:ref:`--password`.
All options other than help options (see :ref:`help-options`) require
an input file. If inspection or JSON options (see
:ref:`inspection-options` and :ref:`json-options`) or help options are
given, an output file must not be given. Otherwise, an output file is
required.
If :samp:`@filename` appears as a word anywhere in the command-line,
it will be read line by line, and each line will be treated as a
command-line argument. Leading and trailing whitespace is
intentionally not removed from lines, which makes it possible to
handle arguments that start or end with spaces. The :samp:`@-` option
allows arguments to be read from standard input. This allows qpdf to
be invoked with an arbitrary number of arbitrarily long arguments. It
is also very useful for avoiding having to pass passwords on the
command line, though see also :qpdf:ref:`--password-file`. Note that
the :samp:`@filename` can't appear in the middle of an argument, so
constructs such as :samp:`--arg=@filename` will not work. Instead, you
would have to include the option and its parameter (e.g.,
:samp:`--option=parameter`) as a line in the :file:`filename` file and
just pass :samp:`@filename` on the command line.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --empty
.. help: use empty file as input
Use in place of infile for an empty input. Especially useful
with --pages.
This option may be given in place of :samp:`{infile}`. This causes
qpdf to use a dummy input file that contains zero pages. This
option is useful in conjunction with :qpdf:ref:`--pages`. See
:ref:`page-selection` for details.
.. qpdf:option:: --replace-input
.. help: overwrite input with output
Use in place of outfile to overwrite the input file with the output.
This option may be given in place of :samp:`{outfile}`. This causes
qpdf to replace the input file with the output. It does this by
writing to :file:`{infilename}.~qpdf-temp#` and, when done,
overwriting the input file with the temporary file. If there were
any warnings, the original input is saved as
:file:`{infilename}.~qpdf-orig`. If there are errors, the input
file is left untouched.
.. qpdf:option:: --job-json-file=file
.. help: job JSON file
Specify the name of a file whose contents are expected to
contain a QPDFJob JSON file. Run qpdf --job-json-help for a
description of the JSON input file format.
Specify the name of a file whose contents are expected to contain a
QPDFJob JSON file. QXXXQ ref. This file is read and treated as if
the equivalent command-line arguments were supplied. It can be
mixed freely with other options.
.. _exit-status:
Exit Status
-----------
.. help-topic exit-status: meanings of qpdf's exit codes
Meaning of exit codes:
0: no errors or warnings
1: not used by qpdf but may be used by the shell if unable to invoke qpdf
2: errors detected
3: warnings detected, unless --warning-exit-0 is given
The exit status of :command:`qpdf` may be interpreted as follows:
.. list-table:: Exit Codes
:widths: 5 80
:header-rows: 0
- - 0
- no errors or warnings were found
- - 1
- not used
- - 2
- errors were found; the file was not processed
- - 3
- warnings were found without errors
Notes:
- A PDF file may have problems that qpdf can't detect.
- With the :qpdf:ref:`--warning-exit-0` option, exit status ``0`` is
used even if there are warnings.
- :command:`qpdf` does not exit with status ``1`` since the shell uses
this exit code if it is unable to invoke the command.
- If both errors and warnings were found, exit status ``2`` is used.
- The :qpdf:ref:`--is-encrypted` and :qpdf:ref:`--requires-password`
options use different exit codes. See their help for details.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --warning-exit-0
.. help: exit 0 even with warnings
Use exit status 0 instead of 3 when warnings are present. When
combined with --no-warn, warnings are completely ignored.
If there were warnings only and no errors, exit with exit code
``0`` instead of ``3``. When combined with :qpdf:ref:`--no-warn`,
the effect is for :command:`qpdf` to completely ignore warnings.
.. _shell-completion:
Shell Completion
----------------
.. help-topic completion: shell completion
Shell completion is supported with bash and zsh. Use
eval $(qpdf --completion-bash) or eval $(qpdf --completion-zsh)
to enable. The QPDF_EXECUTABLE environment variable overrides the
path to qpdf that these commands output.
:command:`qpdf` provides its own completion support for zsh and bash.
You can enable bash completion with :command:`eval $(qpdf
--completion-bash)` and zsh completion with :command:`eval $(qpdf
--completion-zsh)`. If :command:`qpdf` is not in your path, you should
use an absolute path to qpdf in the above invocation. If you invoke it
with a relative path, it will warn you, and the completion won't work
if you're in a different directory.
:command:`qpdf` will use ``argv[0]`` to figure out where its
executable is. This may produce unwanted results in some cases,
especially if you are trying to use completion with a copy of qpdf that
is run directly out of the source tree or that is invoked with a
wrapper script. You can specify a full path to the qpdf you want to
use for completion in the ``QPDF_EXECUTABLE`` environment variable.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --completion-bash
.. help: enable bash completion
Output a command that enables bash completion
Output a completion command you can eval to enable shell completion
from bash.
.. qpdf:option:: --completion-zsh
.. help: enable zsh completion
Output a command that enables zsh completion
Output a completion command you can eval to enable shell completion
from zsh.
.. _help-options:
Help/Information
----------------
.. help-topic help: information about qpdf
Help options provide some information about qpdf itself. Help
options are only valid as the first and only command-line argument.
Help options provide some information about qpdf itself. Help options
are only valid as the first and only command-line argument.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --help[=--option|topic]
.. help: provide help
--help: provide general information and a list of topics
--help=--option: provide help on a specific option
--help=topic: provide help on a topic
Display command-line invocation help. Use :samp:`--help={--option}`
for help on a specific option and :samp:`--help={topic}` for help
on a help topic and also provides a list of available help topics.
.. qpdf:option:: --version
.. help: show qpdf version
Display the version of qpdf.
Display the version of qpdf. The version number displayed is the
one that is compiled into the qpdf library. If you don't see the
version number you expect, you may have more than one version of
:command:`qpdf` installed and may not have your library path set up
correctly.
.. qpdf:option:: --copyright
.. help: show copyright information
Display copyright and license information.
Display copyright and license information.
.. qpdf:option:: --show-crypto
.. help: show available crypto providers
Show a list of available crypto providers, one per line. The
default provider is shown first.
Show a list of available crypto providers, each on a line by
itself. The default provider is always listed first. See
:ref:`crypto` for more information about crypto providers.
.. _general-options:
General Options
---------------
.. help-topic general: general options
General options control qpdf's behavior in ways that are not
directly related to the operation it is performing.
This section describes general options that control :command:`qpdf`'s
behavior. They are not necessarily related to the specific operation
that is being performed and may be used whether or not an output file
is being created.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --password=password
.. help: password for encrypted file
Specify a password for an encrypted, password-protected file.
Not needed for encrypted files without a password.
Specifies a password for accessing encrypted, password-protected
files. To read the password from a file or standard input, you can
use :qpdf:ref:`--password-file`.
Prior to 8.4.0, in the case of passwords that contain characters
that fall outside of 7-bit US-ASCII, qpdf left the burden of
supplying properly encoded encryption and decryption passwords to
the user. Starting in qpdf 8.4.0, qpdf does this automatically in
most cases. For an in-depth discussion, please see
:ref:`unicode-passwords`. Previous versions of this manual
described workarounds using the :command:`iconv` command. Such
workarounds are no longer required or recommended starting with
qpdf 8.4.0. However, for backward compatibility, qpdf attempts to
detect those workarounds and do the right thing in most cases.
.. qpdf:option:: --password-file=filename
.. help: read password from a file
The first line of the specified file is used as the password.
This is used in place of the --password option.
Reads the first line from the specified file and uses it as the
password for accessing encrypted files. :samp:`{filename}` may be
``-`` to read the password from standard input, but if you do that
the password is echoed and there is no prompt, so use ``-`` with
caution. Note that leading and trailing spaces are not stripped
from the password.
.. qpdf:option:: --verbose
.. help: print additional information
Output additional information about various things qpdf is
doing, including information about files created and operations
performed.
Increase verbosity of output. This includes information about files
created, image optimization, and several other operations. In some
cases, it also displays additional information when inspection
options (see :ref:`inspection-options`) are used.
.. qpdf:option:: --progress
.. help: show progress when writing
Indicate progress when writing files.
Indicate progress while writing output files. Progress indication
does not start until writing starts, so there may be a delay before
progress indicators are seen if complicated transformations are
being applied before the write process begins.
.. qpdf:option:: --no-warn
.. help: suppress printing of warning messages
Suppress printing of warning messages. If warnings were
encountered, qpdf still exits with exit status 3.
Use --warning-exit-0 with --no-warn to completely ignore
warnings.
Suppress writing of warnings to stderr. If warnings were detected
and suppressed, :command:`qpdf` will still exit with exit code 3.
To completely ignore warnings, also specify
:qpdf:ref:`--warning-exit-0`. Use with caution as qpdf is not
always successful in recovering from situations that cause warnings
to be issued.
.. qpdf:option:: --deterministic-id
.. help: generate ID deterministically
Generate a secure, random document ID only using static
information, such as the page contents. Does not use the file's
name or attributes or the current time.
Generate a secure, random document ID using deterministic values.
This prevents use of timestamp and output file name information in
the ID generation. Instead, at some slight additional runtime cost,
the ID field is generated to include a digest of the significant
parts of the content of the output PDF file. This means that a
given qpdf operation should generate the same ID each time it is
run, which can be useful when caching results or for generation of
some test data. Use of this flag is not compatible with creation of
encrypted files. This option can be useful for testing. See also
:qpdf:ref:`--static-id`.
While qpdf will generate the same deterministic ID given the same
output PDF, there is no guarantee that different versions of qpdf
will generate exactly the same PDF output for the same input and
options. While care is taken to avoid gratuitous changes to qpdf's
PDF generation, new versions of qpdf may include changes or bug
fixes that cause slightly different PDF code to be generated. Such
changes are noted in the release notes.
.. qpdf:option:: --allow-weak-crypto
.. help: allow insecure cryptographic algorithms
Allow creation of files with weak cryptographic algorithms. This
option is necessary to create 40-bit files or 128-bit files that
use RC4 encryption.
Starting with version 10.4, qpdf issues warnings when requested to
create files using RC4 encryption. This option suppresses those
warnings. In future versions of qpdf, qpdf will refuse to create
files with weak cryptography when this flag is not given. See
:ref:`weak-crypto` for additional details.
.. qpdf:option:: --keep-files-open=[y|n]
.. help: manage keeping multiple files open
When qpdf needs to work with many files, as when merging large
numbers of files, explicitly indicate whether files should be
kept open. The default behavior is to determine this based on
the number of files.
This option controls whether qpdf keeps individual files open while
merging. By default, qpdf keeps files open when merging unless more
than 200 files are specified, in which case files are opened as
needed and closed when finished. Repeatedly opening
and closing files may impose a large performance penalty with some
file systems, especially networked file systems. If you know that
you have a large enough open file limit and are suffering from
performance problems, or if you have an open file limit smaller
than 200, you can use this option to override the default behavior
by specifying :samp:`--keep-files-open=y` to force :command:`qpdf`
to keep files open or :samp:`--keep-files-open=n` to force it to
only open files as needed. See also
:qpdf:ref:`--keep-files-open-threshold`.
Historical note: prior to version 8.1.0, qpdf always kept all files
open, but this meant that the number of files that could be merged
was limited by the operating system's open file limit. Version
8.1.0 opened files as they were referenced and closed them after
each read, but this caused a major performance impact. Version
8.2.0 optimized the performance but did so in a way that, for local
file systems, there was a small but unavoidable performance hit,
but for networked file systems the performance impact could be
very high. The current behavior was introduced in qpdf version
8.2.1.
.. qpdf:option:: --keep-files-open-threshold=count
.. help: set threshold for --keep-files-open
Set the threshold used by --keep-files-open, overriding the
default value of 200.
If specified, overrides the default value of 200 used as the
threshold for qpdf deciding whether or not to keep files open. See
:qpdf:ref:`--keep-files-open` for details.
.. _advanced-control-options:
Advanced Control Options
------------------------
.. help-topic advanced-control: tweak qpdf's behavior
Advanced control options control qpdf's behavior in ways that would
normally never be needed by a user but that may be useful to
developers or people investigating problems with specific files.
Advanced control options control qpdf's behavior in ways that would
normally never be needed by a user but that may be useful to
developers or people investigating problems with specific files.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --password-is-hex-key
.. help: provide hex-encoded encryption key
Provide the underlying file encryption key as a hex-encoded
string rather than supplying a password. This is an expert
option.
Overrides the usual computation/retrieval of the PDF file's
encryption key from user/owner password with an explicit
specification of the encryption key. When this option is specified,
the parameter to the :qpdf:ref:`--password` option is interpreted as
a hexadecimal-encoded key value. This only applies to the password
used to open the main input file. It does not apply to other files
opened by :qpdf:ref:`--pages` or other options or to files being
written.
Most users will never have a need for this option, and no standard
viewers support this mode of operation, but it can be useful for
forensic or investigatory purposes. For example, if a PDF file is
encrypted with an unknown password, a brute-force attack using the
key directly is sometimes more efficient than one using the
password. Also, if a file is heavily damaged, it may be possible to
derive the encryption key and recover parts of the file using it
directly. To expose the encryption key used by an encrypted file
that you can open normally, use the
:qpdf:ref:`--show-encryption-key` option.
.. qpdf:option:: --suppress-password-recovery
.. help: don't try different password encodings
Suppress qpdf's usual behavior of attempting different encodings
of a password that contains non-ASCII Unicode characters if the
first attempt doesn't succeed.
Ordinarily, qpdf attempts to automatically compensate for passwords
encoded with the wrong character encoding. This option suppresses
that behavior. Under normal conditions, there are no reasons to use
this option. See :ref:`unicode-passwords` for a discussion.
.. qpdf:option:: --password-mode=mode
.. help: tweak how qpdf encodes passwords
Fine-tune how qpdf controls encoding of Unicode passwords. Valid
options are auto, bytes, hex-bytes, and unicode.
This option can be used to fine-tune how qpdf interprets Unicode
(non-ASCII) password strings passed on the command line. With the
exception of the :samp:`hex-bytes` mode, these only apply to
passwords provided when encrypting files. The :samp:`hex-bytes`
mode also applies to passwords specified for reading files. For
additional discussion of the supported password modes and when you
might want to use them, see :ref:`unicode-passwords`. The following
modes are supported:
- :samp:`auto`: Automatically determine whether the specified
password is a properly encoded Unicode (UTF-8) string, and
transcode it as required by the PDF spec based on the type of
encryption being applied. On Windows starting with version 8.4.0,
and on almost all other modern platforms, incoming passwords will
be properly encoded in UTF-8, so this is almost always what you
want.
- :samp:`unicode`: Tells qpdf that the incoming password is UTF-8,
overriding whatever its automatic detection determines. The only
difference between this mode and :samp:`auto` is that qpdf will
fail with an error message if the password is not valid UTF-8
instead of falling back to :samp:`bytes` mode with a warning.
- :samp:`bytes`: Interpret the password as a literal byte string.
For non-Windows platforms, this is what versions of qpdf prior to
8.4.0 did. For Windows platforms, there is no way to specify
strings of binary data on the command line directly, but you can
use a :samp:`@filename` option or :qpdf:ref:`--password-file` to
do it, in which case this option forces qpdf to respect the
string of bytes as provided. Note that this option may cause you
to encrypt PDF files with passwords that will not be usable by
other readers.
- :samp:`hex-bytes`: Interpret the password as a hex-encoded
string. This provides a way to pass binary data as a password on
all platforms including Windows. As with :samp:`bytes`, this
option may allow creation of files that can't be opened by other
readers. This mode affects qpdf's interpretation of passwords
specified for decrypting files as well as for encrypting them. It
makes it possible to specify strings that are encoded in some
manner other than the system's default encoding.
.. qpdf:option:: --suppress-recovery
.. help: suppress error recovery
Avoid attempting to recover when errors are found in a file's
cross reference table or stream lengths.
Prevents qpdf from attempting to reconstruct a file's cross
reference table when there are errors reading objects from the
file. Recovery is triggered by a variety of situations. While
usually successful, it uses heuristics that don't work on all
files. If this option is given, :command:`qpdf` fails on the first
error it encounters.
.. qpdf:option:: --ignore-xref-streams
.. help: use xref tables rather than streams
Ignore any cross-reference streams in the file, falling back to
cross-reference tables or triggering document recovery.
Tells qpdf to ignore any cross-reference streams, falling back to
any embedded cross-reference tables or triggering document
recovery. Ordinarily, qpdf reads cross-reference streams when they
are present in a PDF file. If this option is specified,
qpdf will ignore any cross-reference streams for hybrid PDF files.
The purpose of hybrid files is to make some content available to
viewers that are not aware of cross-reference streams. It is almost
never desirable to ignore them. The only time when you might want
to use this feature is if you are testing creation of hybrid PDF
files and wish to see how a PDF consumer that doesn't understand
object and cross-reference streams would interpret such a file.
.. _transformation-options:
PDF Transformation
------------------
.. help-topic transformation: make structural PDF changes
The options below tell qpdf to apply transformations that change
the structure without changing the content.
The options discussed in this section tell qpdf to apply
transformations that change the structure of a PDF file without
changing its content. Examples include creating linearized
(web-optimized) files, adding or removing encryption, restructuring
files for older viewers, and rewriting files for human inspection. See
also :ref:`modification-options`.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --linearize
.. help: linearize (web-optimize) output
Create linearized (web-optimized) output files.
Create linearized (web-optimized) output files. Linearized files
are formatted in a way that allows compliant readers to begin
displaying a PDF file before it is fully downloaded. Ordinarily,
the entire file must be present before it can be rendered because
important cross-reference information typically appears at the end
of the file.
.. qpdf:option:: --encrypt user-password owner-password key-length [options] --
.. help: start encryption options
Run qpdf --help=encryption for details.
This flag starts encryption options, used to create encrypted
files. Please see :ref:`encryption-options` for details.
.. qpdf:option:: --decrypt
.. help: remove encryption from input file
Create an unencrypted output file even if the input file was
encrypted. Normally qpdf preserves whatever encryption was
present on the input file. This option overrides that behavior.
Create an output file with no encryption even if the input file is
encrypted. This option overrides the default behavior of preserving
whatever encryption was present on the input file. This
functionality is not intended to be used for bypassing copyright
restrictions or other restrictions placed on files by their
producers. See also :qpdf:ref:`--copy-encryption`.
.. qpdf:option:: --copy-encryption=file
.. help: copy another file's encryption details
Copy encryption details from the specified file instead of
preserving the input file's encryption. Use --encryption-file-password
to specify the encryption file's password.
Copy all encryption parameters, including the user password, the
owner password, and all security restrictions, from the specified
file instead of preserving the encryption details from the input
file. This works even if only one of the user password or owner
password is known. If the encryption file requires a password, use
the :qpdf:ref:`--encryption-file-password` option to set it. Note
that copying the encryption parameters from a file also copies the
first half of ``/ID`` from the file since this is part of the
encryption parameters. This option can be useful if you need to
decrypt a file to make manual changes to it or to change it outside
of qpdf, and then want to restore the original encryption on the
file without having to manual specify all the individual settings.
See also :qpdf:ref:`--decrypt`.
.. qpdf:option:: --encryption-file-password=password
.. help: supply password for --copy-encryption
If the file named in --copy-encryption requires a password, use
this option to supply the password.
If the file specified with :qpdf:ref:`--copy-encryption`
requires a password, supply the password using this option. This
option is necessary because the :qpdf:ref:`--password` option
applies to the input file, not the file from which encryption is
being copied.
.. qpdf:option:: --qdf
.. help: enable viewing PDF code in a text editor
Create a PDF file suitable for viewing in a text editor and even
editing. This is for editing the PDF code, not the page contents.
All streams that can be uncompressed are uncompressed, and
content streams are normalized, among other changes. The
companion tool "fix-qdf" can be used to repair hand-edited QDF
files. QDF is a feature specific to the qpdf tool. Please see
the "QDF Mode" chapter in the manual.
Create a PDF file suitable for viewing and editing in a text
editor. This is to edit the PDF code, not the page contents. To
edit a QDF file, your text editor must preserve binary data. In a
QDF file, all streams that can be uncompressed are uncompressed,
and content streams are normalized, among other changes. The
companion tool :command:`fix-qdf` can be used to repair hand-edited
QDF files. QDF is a feature specific to the qpdf tool. For
additional information, see :ref:`qdf`. Note that
:qpdf:ref:`--linearize` disables QDF mode.
QDF mode has full support for object streams, but sometimes it's
easier to locate a specific object if object streams are disabled.
When trying to understand some PDF construct by inspecting an
existing file, it can be useful to combine :samp:`--qdf` with
:samp:`--object-streams=disable`.
This flag changes some of the defaults of other options: stream
data is uncompressed, content streams are normalized, and
encryption is removed. These defaults can still be overridden by
specifying the appropriate options with :samp:`--qdf`.
Additionally, in QDF mode, stream lengths are stored as indirect
objects, objects are formatted in a less efficient but more
readable fashion, and the documents are interspersed with comments
that make it easier for the user to find things and also make it
possible for :command:`fix-qdf` to work properly. When editing QDF
files, it is not necessary to maintain the object formatting.
When normalizing content, if qpdf runs into any lexical errors, it
will print a warning indicating that content may be damaged. If you
want to create QDF files without content normalization, specify
:samp:`--qdf --normalize-content=n`. You can also create a non-QDF
file with uncompressed streams using
:samp:`--stream-data=uncompress`. Either option will uncompress all
the streams but will not attempt to normalize content. Please note
that if you are using content normalization or QDF mode for the
purpose of manually inspecting files, you don't have to care about
this.
See also :qpdf:ref:`--no-original-object-ids`.
.. qpdf:option:: --no-original-object-ids
.. help: omit original object IDs in qdf
Omit comments in a QDF file indicating the object ID an object
had in the original file.
Suppresses inclusion of original object ID comments in QDF files.
This can be useful when generating QDF files for test purposes,
particularly when comparing them to determine whether two PDF files
have identical content. The original object ID comment is there by
default because it makes it easier to trace objects back to the
original file.
.. qpdf:option:: --compress-streams=[y|n]
.. help: compress uncompressed streams
Setting --compress-streams=n prevents qpdf from compressing
uncompressed streams. This can be useful if you are leaving some
streams uncompressed intentionally.
By default, or with :samp:`--compress-streams=y`, qpdf will
compress streams using the flate compression algorithm (used by zip
and gzip) unless those streams are compressed in some other way.
This analysis is made after qpdf attempts to uncompress streams and
is therefore closely related to :qpdf:ref:`--decode-level`. To
suppress this behavior and leave streams streams uncompressed, use
:samp:`--compress-streams=n`. In QDF mode (see :ref:`qdf` and
:qpdf:ref:`--qdf`), the default is to leave streams uncompressed.
.. qpdf:option:: --decode-level=parameter
.. help: control which streams to uncompress
When uncompressing streams, control which types of compression
schemes should be uncompressed:
- none: don't uncompress anything
- generalized: uncompress streams compressed with a
general-purpose compression algorithm. This is the default.
- specialized: in addition to generalized, also uncompress
streams compressed with a special-purpose but non-lossy
compression scheme
- all: in addition to specialized, uncompress streams compressed
with lossy compression schemes like JPEG (DCT)
qpdf does not know how to uncompress all compression schemes.
Controls which streams qpdf tries to decode. The default is
:samp:`generalized`.
The following values for :samp:`{parameter}` are available:
- :samp:`none`: do not attempt to decode any streams
- :samp:`generalized`: decode streams filtered with supported
generalized filters: ``/LZWDecode``, ``/FlateDecode``,
``/ASCII85Decode``, and ``/ASCIIHexDecode``. We define
generalized filters as those to be used for general-purpose
compression or encoding, as opposed to filters specifically
designed for image data.
- :samp:`specialized`: in addition to generalized, decode streams
with supported non-lossy specialized filters; currently this is
just ``/RunLengthDecode``
- :samp:`all`: in addition to generalized and specialized, decode
streams with supported lossy filters; currently this is just
``/DCTDecode`` (JPEG)
There are several filters that :command:`qpdf` does not support.
These are left untouched regardless of the option. Future versions
of qpdf may support additional filters.
Because the default value is ``generalized``, qpdf's default
behavior is to uncompress any stream that is encoded using
non-lossy filters that qpdf understands. If
``--compress-streams=y`` is also in effect, which is the default
(see :qpdf:ref:`--compress-streams`), the overall effect is that
qpdf will recompress streams with generalized filters using flate
compression, effectively eliminating LZW and ASCII-based filters.
This is usually desirable behavior but can be disabled with
``--decode-level=none``.
As a special case, streams already compressed with ``/FlateDecode``
are not uncompressed and recompressed. You can change this behavior
with :qpdf:ref:`--recompress-flate`.
.. qpdf:option:: --stream-data=parameter
.. help: control stream compression
This option controls how streams are compressed in the output.
It is less granular than the newer options, --compress-streams
and --decode-level.
Parameters:
- compress: same as --compress-streams=y --decode-level=generalized
- preserve: same as --compress-streams=n --decode-level=none
- uncompress: same as --compress-streams=n --decode-level=generalized
Controls transformation of stream data. This option predates the
:qpdf:ref:`--compress-streams` and :qpdf:ref:`--decode-level`
options. Those options can be used to achieve the same effect with
more control. The value of :samp:`{parameter}` may be one of the
following:
- :samp:`compress`: recompress stream data when possible (default);
equivalent to :samp:`--compress-streams=y`
:samp:`--decode-level=generalized`. Does not recompress streams
already compressed with ``/FlateDecode`` unless
:qpdf:ref:`--recompress-flate` is also specified.
- :samp:`preserve`: leave all stream data as is; equivalent to
:samp:`--compress-streams=n` :samp:`--decode-level=none`
- :samp:`uncompress`: uncompress stream data compressed with
generalized filters when possible; equivalent to
:samp:`--compress-streams=n` :samp:`--decode-level=generalized`
.. qpdf:option:: --recompress-flate
.. help: uncompress and recompress flate
The default generalized compression scheme used by PDF is flate,
which is the same as used by zip and gzip. Usually qpdf just
leaves these alone. This option tells qpdf to uncompress and
recompress streams compressed with flate. This can be useful
when combined with --compression-level.
The default generalized compression scheme used by PDF is flate
(``/FlateDecode``), which is the same as used by :command:`zip` and
:command:`gzip`. Usually qpdf just leaves these alone. This option
tells :command:`qpdf` to uncompress and recompress streams
compressed with flate. This can be useful when combined with
:qpdf:ref:`--compression-level`. Using this option may make
:command:`qpdf` much slower when writing output files.
.. qpdf:option:: --compression-level=level
.. help: set compression level for flate
Set a compression level from 1 (least, fastest) to 9 (most,
slowest) when compressing files with flate (used in zip and
gzip), which is the default compression for most PDF files.
You need --recompress-flate with this option if you want to
change already compressed streams.
When writing new streams that are compressed with ``/FlateDecode``,
use the specified compression level. The value of :samp:`level`
should be a number from 1 to 9 and is passed directly to zlib,
which implements deflate compression. Lower numbers compress less
and are faster; higher numbers compress more and are slower. Note
that :command:`qpdf` doesn't uncompress and recompress streams
compressed with flate by default. To have this option apply to
already compressed streams, you should also specify
:qpdf:ref:`--recompress-flate`. If your goal is to shrink the size
of PDF files, you should also use
:samp:`--object-streams=generate`. If you omit this option, qpdf
defers to the compression library's default behavior.
.. qpdf:option:: --normalize-content=[y|n]
.. help: fix newlines in content streams
Normalize newlines to UNIX-style newlines in PDF content
streams, which is useful for viewing them in a programmer's text
editor across multiple platforms. This is also turned on by
--qdf.
Enables or disables normalization of newlines in PDF content
streams to UNIX-style newlines, which is useful for viewing files
in a programmer-friendly text edit across multiple platforms.
Content normalization is off by default, but is automatically
enabled by :qpdf:ref:`--qdf` (see also :ref:`qdf`). It is not
recommended to use this option for production use. If qpdf runs
into any lexical errors while normalizing content, it will print a
warning indicating that content may be damaged.
.. qpdf:option:: --object-streams=mode
.. help: control use of object streams
Control what qpdf does regarding object streams. Options:
- preserve: preserve original object streams, if any (the default)
- disable: create output files with no object streams
- generate: create object streams, and compress objects when possible
Controls handling of object streams. The value of :samp:`{mode}`
may be one of the following:
.. list-table:: Object Stream Modes
:widths: 10 80
:header-rows: 0
- - :samp:`preserve`
- preserve original object streams, if any (the default)
- - :samp:`disable`
- create output files with no object streams
- - :samp:`generate`
- create object streams, and compress objects when possible
Object streams are PDF streams that contain other objects. Putting
objects into object streams allows the PDF objects themselves to be
compressed, which can result in much smaller PDF files. Combining
this option with :qpdf:ref:`--compression-level` and
:qpdf:ref:`--recompress-flate` can often result in the creation of
smaller PDF files.
Object streams, also known as compressed objects, were introduced
into the PDF specification at version 1.5 around 2003. Some ancient
PDF viewers may not support files with object streams. qpdf can be
used to transform files with object streams into files without object
streams or vice versa.
In :samp:`preserve` mode, the relationship between objects and the
streams that contain them is preserved from the original file. If
the file has no object streams, qpdf will not add any. In
:samp:`disable` mode, all objects are written as regular,
uncompressed objects. The resulting file should be structurally
readable by older PDF viewers, though there is still a chance that
the file may contain other content that some older readers can't
support. In :samp:`generate` mode, qpdf will create its own object
streams. This will usually result in more compact PDF files. In
this mode, qpdf will also make sure the PDF version number in the
header is at least 1.5.
.. qpdf:option:: --preserve-unreferenced
.. help: preserve unreferenced objects
Preserve all objects from the input even if not referenced.
Tells qpdf to preserve objects that are not referenced when writing
the file. Ordinarily any object that is not referenced in a
traversal of the document from the trailer dictionary will be
discarded. Disabling this default behavior may be useful in working
with some damaged files or inspecting files with known unreferenced
objects.
This flag is ignored for linearized files and has the effect of
causing objects in the new file to be written ordered by object ID
from the original file. This does not mean that object numbers will
be the same since qpdf may create stream lengths as direct or
indirect differently from the original file, and the original file
may have gaps in its numbering.
See also :qpdf:ref:`--preserve-unreferenced-resources`, which does
something completely different.
.. qpdf:option:: --remove-unreferenced-resources=parameter
.. help: remove unreferenced page resources
Remove from a page's resource dictionary any resources that are
not referenced in the page's contents. Parameters: "auto"
(default), "yes", "no".
Parameters: ``auto`` (the default), ``yes``, or ``no``.
Starting with qpdf 8.1, when splitting pages, qpdf is able to
attempt to remove images and fonts that are not used by a page even
if they are referenced in the page's resources dictionary. When
shared resources are in use, this behavior can greatly reduce the
file sizes of split pages, but the analysis is very slow. In
versions from 8.1 through 9.1.1, qpdf did this analysis by default.
Starting in qpdf 10.0.0, if ``auto`` is used, qpdf does a quick
analysis of the file to determine whether the file is likely to
have unreferenced objects on pages, a pattern that frequently
occurs when resource dictionaries are shared across multiple pages
and rarely occurs otherwise. If it discovers this pattern, then it
will attempt to remove unreferenced resources. Usually this means
you get the slower splitting speed only when it's actually going to
create smaller files. You can suppress removal of unreferenced
resources altogether by specifying ``no`` or force qpdf to do the
full algorithm by specifying ``yes``.
Other than cases in which you don't care about file size and care a
lot about runtime, there are few reasons to use this option,
especially now that ``auto`` mode is supported. One reason to use
this is if you suspect that qpdf is removing resources it shouldn't
be removing. If you encounter such a case, please report it as a bug at
https://github.com/qpdf/qpdf/issues/.
.. qpdf:option:: --preserve-unreferenced-resources
.. help: use --remove-unreferenced-resources=no
Synonym for --remove-unreferenced-resources=no. Use that instead.
This is a synonym for :samp:`--remove-unreferenced-resources=no`.
See :qpdf:ref:`--remove-unreferenced-resources`.
See also :qpdf:ref:`--preserve-unreferenced`, which does something
completely different. To reduce confusion, you should use
:samp:`--remove-unreferenced-resources=no` instead.
.. qpdf:option:: --newline-before-endstream
.. help: force a newline before endstream
For an extra newline before endstream. Using this option enables
qpdf to preserve PDF/A when rewriting such files.
Tell qpdf to insert a newline before the ``endstream`` keyword,
not counted in the length, after any stream content even if the
last character of the stream was a newline. This may result in two
newlines in some cases. This is a requirement of PDF/A. While qpdf
doesn't specifically know how to generate PDF/A-compliant PDFs,
this at least prevents it from removing compliance on already
compliant files.
.. qpdf:option:: --coalesce-contents
.. help: combine content streams
If a page has an array of content streams, concatenate them into
a single content stream.
When a page's contents are split across multiple streams, this
option causes qpdf to combine them into a single stream. Use of
this option is never necessary for ordinary usage, but it can help
when working with some files in some cases. For example, this can
be combined with QDF mode or content normalization to make it
easier to look at all of a page's contents at once. It is common
for PDF writers to create multiple content streams for a variety of
reasons such as making it easier to modify page contents and
splitting very large content streams so PDF viewers may be able to
use less memory.
.. qpdf:option:: --externalize-inline-images
.. help: convert inline to regular images
Convert inline images to regular images.
Convert inline images to regular images. By default, images whose
data is at least 1,024 bytes are converted when this option is
selected. Use :qpdf:ref:`--ii-min-bytes` to change the size
threshold. This option is implicitly selected when
:qpdf:ref:`--optimize-images` is selected unless
:qpdf:ref:`--keep-inline-images` is also specified.
.. qpdf:option:: --ii-min-bytes=size-in-bytes
.. help: set minimum size for --externalize-inline-images
Don't externalize inline images smaller than this size. The
default is 1,024. Use 0 for no minimum.
Avoid converting inline images whose size is below the specified
minimum size to regular images. The default is 1,024 bytes. Use 0
for no minimum.
.. qpdf:option:: --min-version=version
.. help: set minimum PDF version
Force the PDF version of the output to be at least the specified
version. The version number format is
"major.minor[.extension-level]", which sets the version header
to "major.minor" and the extension level, if specified, to
"extension-level".
Force the PDF version of the output file to be at least
:samp:`{version}`. In other words, if the input file has a lower
version than the specified version, the specified version will be
used. If the input file has a higher version, the input file's
original version will be used. It is seldom necessary to use this
option since qpdf will automatically increase the version as needed
when adding features that require newer PDF readers.
The version number may be expressed in the form
:samp:`{major}.{minor}[.{extension-level}]`. If
:samp:`.{extension-level}`, is given, version is interpreted as
:samp:`{major.minor}` at extension level :samp:`{extension-level}`.
For example, version ``1.7.8`` represents version 1.7 at extension
level 8. Note that minimal syntax checking is done on the command
line. :command:`qpdf` does not check whether the specified version
is actually required.
.. qpdf:option:: --force-version=version
.. help: set output PDF version
Force the output PDF file's PDF version header to be the specified
value, even if the file uses features that may not be available
in that version.
This option forces the PDF version to be the exact version
specified *even when the file may have content that is not
supported in that version*. The version number is interpreted in
the same way as with :qpdf:ref:`--min-version` so that extension
levels can be set. In some cases, forcing the output file's PDF
version to be lower than that of the input file will cause qpdf to
disable certain features of the document. Specifically, 256-bit
keys are disabled if the version is less than 1.7 with extension
level 8 (except the deprecated, unsupported "R5" format is allowed
with extension levels 3 through 7), AES encryption is disabled if
the version is less than 1.6, cleartext metadata and object streams
are disabled if less than 1.5, 128-bit encryption keys are disabled
if less than 1.4, and all encryption is disabled if less than 1.3.
Even with these precautions, qpdf won't be able to do things like
eliminate use of newer image compression schemes, transparency
groups, or other features that may have been added in more recent
versions of PDF.
As a general rule, with the exception of big structural things like
the use of object streams or AES encryption, PDF viewers are
supposed to ignore features they don't support. This means that
forcing the version to a lower version may make it possible to open
your PDF file with an older version, though bear in mind that some
of the original document's functionality may be lost.
.. _page-ranges:
Page Ranges
-----------
.. help-topic page-ranges: page range syntax
A full description of the page range syntax, with examples, can be
found in the manual. Summary:
- a,b,c pages a, b, and c
- a-b pages a through b inclusive; if a > b, this counts down
- r<n> where <n> represents a number is the <n>th page from the end
- z the last page, same as r1
You can append :even or :odd to select every other page from the
resulting set of pages, where :odd starts with the first page and
:even starts with the second page. These are odd and even pages
from the resulting set, not based on the original page numbers.
Several :command:`qpdf` command-line options use page ranges. This
section describes the syntax of a page range.
- A plain number indicates a page numbered from ``1``, so ``1``
represents the first page.
- A number preceded by ``r`` counts from the end, so ``r1`` is the
last page, ``r2`` is the second-to-last page, etc.
- The letter ``z`` represents the last page and is the same as ``r1``.
- Page numbers may appear in any order separated by commas.
- Two page numbers separated by dashes represents the inclusive range
of pages from the first to the second. If the first number is higher
than the second number, it is the range of pages in reverse.
- The range may be appended with ``:odd`` or ``:even`` to select only
pages from the resulting range in odd or even positions. In this
case, odd and even refer to positions in the final range, not
whether the original page number is odd or even.
.. list-table:: Example Page Ranges
:widths: 20 80
:header-rows: 0
- - ``1,6,4``
- pages 1, 6, and 4 in that order
- - ``3-7``
- pages 3 through 7 inclusive in increasing order
- - ``7-3``
- pages 7, 6, 5, 4, and 3 in that order
- - ``1-z``
- all pages in order
- - ``z-1``
- all pages in reverse order
- - ``1,3,5-9,15-12``
- pages 1, 3, 5, 6, 7, 8, 9, 15, 14, 13, and 12 in that order
- - ``r3-r1``
- the last three pages of the document
- - ``r1-r3``
- the last three pages of the document in reverse order
- - ``1-20:even``
- even pages from 2 to 20
- - ``5,7-9,12``
- pages 5, 7, 8, 9, and 12
- - ``5,7-9,12:odd``
- pages 5, 8, and 12, which are the pages in odd positions from
the original set of 5, 7, 8, 9, 12
- - ``5,7-9,12:even``
- pages 7 and 9, which are the pages in even positions from the
original set of 5, 7, 8, 9, 12
.. _modification-options:
PDF Modification
----------------
.. help-topic modification: change parts of the PDF
Modification options make systematic changes to certain parts of
the PDF, causing the PDF to render differently from the original.
Modification options make systematic changes to certain parts of the
PDF, causing the PDF to render differently from the original. See also
:ref:`transformation-options`.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --pages file [--password=password] [page-range] [...] --
.. help: begin page selection
Run qpdf --help=page-selection for details.
This flag starts page selection options, which are used to select
pages from one or more input files to perform operations such as
splitting, merging, and collating files.
Please see :ref:`page-selection` for details about selecting pages.
See also :qpdf:ref:`--split-pages`, :qpdf:ref:`--collate`,
:ref:`page-ranges`.
.. qpdf:option:: --collate[=n]
.. help: collate with --pages
Collate rather than concatenate pages specified with --pages.
With a numeric parameter, collate in groups of n. The default
is 1. Run qpdf --help=page-selection for additional details.
This option causes :command:`qpdf` to collate rather than
concatenate pages specified with :qpdf:ref:`--pages`. With a
numeric parameter, collate in groups of :samp:`{n}`. The default
is 1.
Please see :ref:`page-selection` for additional details.
.. qpdf:option:: --split-pages[=n]
.. help: write pages to separate files
This option causes qpdf to create separate output files for each
page or group of pages rather than a single output file.
File names are generated from the specified output file as follows:
- If the string %d appears in the output file name, it is replaced with a
zero-padded page range starting from 1
- Otherwise, if the output file name ends in .pdf (case insensitive), a
zero-padded page range, preceded by a dash, is inserted before the file
extension
- Otherwise, the file name is appended with a zero-padded page range
preceded by a dash.
Page ranges are single page numbers for single-page groups or first-last
for multi-page groups.
Write each group of :samp:`{n}` pages to a separate output file. If
:samp:`{n}` is not specified, create single pages. Output file
names are generated as follows:
- If the string ``%d`` appears in the output file name, it is
replaced with a range of zero-padded page numbers starting
from 1.
- Otherwise, if the output file name ends in :file:`.pdf` (case
insensitive), a zero-padded page range, preceded by a dash, is
inserted before the file extension.
- Otherwise, the file name is appended with a zero-padded page
range preceded by a dash.
Zero padding is added to all page numbers in file names so that all
the numbers are the same length, which causes the output filenames
to sort lexically in numerical order.
Page ranges are a single number in the case of single-page groups or
two numbers separated by a dash otherwise.
Here are some examples. In these examples, :file:`infile.pdf` has
12 pages.
- ``qpdf --split-pages infile.pdf %d-out``: output files are
:file:`01-out` through :file:`12-out` with no extension.
- ``qpdf --split-pages=2 infile.pdf outfile.pdf``: output files are
:file:`outfile-01-02.pdf` through :file:`outfile-11-12.pdf`
- ``qpdf --split-pages infile.pdf something.else`` would generate
files :file:`something.else-01` through
:file:`something.else-12`. The extension ``.else`` is not treated
in any special way regarding the placement of the number.
Note that outlines, threads, and other document-level features of
the original PDF file are not preserved. For each page of output,
this option creates an empty PDF and copies a single page from the
output into it. If you require the document-level data, you will
have to run :command:`qpdf` with the :qpdf:ref:`--pages` option
once for each page. Using :qpdf:ref:`--split-pages` is much faster
if you don't require the document-level data. A future version of
qpdf may support preservation of some document-level information.
.. qpdf:option:: --overlay file [options] --
.. help: begin overlay options
Overlay pages from another file on the output.
Run qpdf --help=overlay-underlay for details.
Overlay pages from another file on the output.
See :ref:`overlay-underlay` for details.
.. qpdf:option:: --underlay file [options] --
.. help: begin underlay options
Underlay pages from another file on the output.
Run qpdf --help=overlay-underlay for details.
Underlay pages from another file on the output.
See :ref:`overlay-underlay` for details.
.. qpdf:option:: --flatten-rotation
.. help: remove rotation from page dictionary
For each page that is rotated using the /Rotate key in the
page's dictionary, remove the /Rotate key and implement the
identical rotation semantics by modifying the page's contents.
This can be useful if a broken PDF viewer fails to properly
consider page rotation metadata.
For each page that is rotated using the ``/Rotate`` key in the
page's dictionary, remove the ``/Rotate`` key and implement the
identical rotation semantics by modifying the page's contents. This
option can be useful to prepare files for buggy PDF applications
that don't properly handle rotated pages. There is usually no
reason to use this option unless you are working around a specific
problem.
.. qpdf:option:: --flatten-annotations=parameter
.. help: push annotations into content
Push page annotations into the content streams. This may be
necessary in some case when printing or splitting files.
Parameters: "all", "print", "screen".
This option collapses annotations into the pages' contents with
special handling for form fields. Ordinarily, an annotation is
rendered separately and on top of the page. Combining annotations
into the page's contents effectively freezes the placement of the
annotations, making them look right after various page
transformations. The library functionality backing this option was
added for the benefit of programs that want to create *n-up* page
layouts and other similar things that don't work well with
annotations. The value of :samp:`{parameter}` may be any of the
following:
.. list-table:: Flatten Annotation Parameters
:widths: 10 80
:header-rows: 0
- - :samp:`all`
- include all annotations that are not marked invisible or
hidden
- - :samp:`print`
- only include annotations that should appear when the page is
printed
- - :samp:`screen`
- omit annotations that should not appear on the screen
In a PDF file, interactive form fields have a value and,
independently, a set of instructions, called an appearance, to
render the filled-in field. If a form is filled in by a program
that doesn't know how to update the appearances, they may become
inconsistent with the fields' values. If qpdf detects this case,
its default behavior is not to flatten those annotations because
doing so would cause the value of the form field to be lost. This
gives you a chance to go back and resave the form with a program
that knows how to generate appearances. qpdf itself can generate
appearances with some limitations. See the
:qpdf:ref:`--generate-appearances` option for details.
.. qpdf:option:: --rotate=[+|-]angle[:page-range]
.. help: rotate pages
Rotate specified pages by multiples of 90 degrees specifying
either absolute or relative angles. "angle" may be 0, 90, 180,
or 270. You almost always want to use +angle or -angle rather
than just angle, as discussed in the manual. Run
qpdf --help=page-ranges for help with page ranges.
Rotate the specified range of pages by the specified angle, which
must be a multiple of 90 degrees.
The value of :samp:`{angle}` may be ``0``, ``90``, ``180``, or ``270``.
For a description of the syntax of :samp:`{page-range}`, see
:ref:`page-ranges`. If the page range is omitted, the rotation is
applied to all pages.
If ``+`` is prepended to :samp:`{angle}`, the angle is added, so an
angle of ``+90`` indicates a 90-degree clockwise rotation. If ``-``
is prepended, the angle is subtracted, so ``-90`` is a 90-degree
counterclockwise rotation and is exactly the same as ``+270``.
If neither ``+`` or ``-`` is prepended, the rotation angle is set
exactly. You almost always want ``+`` or ``-`` since, without
inspecting the actual PDF code, it is impossible to know whether a
page that appears to be rotate is rotated "naturally" or has been
rotated by specifying rotation. For example, if a page appears to
contain a portrait-mode image rotated by 90 degrees so that the top
of the image is on the right edge of the page, there is no way to
tell by visual inspection whether the literal top of the image is
the top of the page or whether the literal top of the image is the
right edge and the page is already rotated in the PDF. Specifying a
rotation angle of ``-90`` will produce an image that appears
upright in either case. Use of absolute rotation angles should be
reserved for cases in which you have specific knowledge about the
way the PDF file is constructed.
Examples:
- ``qpdf in.pdf out.pdf --rotate=+90:2,4,6 --rotate=+180:7-8``:
rotate pages 2, 4, and 6 by 90 degrees clockwise from their
original rotation
- ``qpdf in.pdf out.pdf --rotate=+180``: rotate all pages by 180
degrees
- ``qpdf in.pdf out.pdf --rotate=0``: force each page to be displayed
in its natural orientation, which would undo the effect of any
rotations previously applied in page metadata.
See also :qpdf:ref:`--flatten-rotation`.
.. qpdf:option:: --generate-appearances
.. help: generate appearances for form fields
PDF form fields consist of values and appearances, which may be
inconsistent with each other if a form field value has been
modified without updating its appearance. This option tells qpdf
to generate new appearance streams. There are some limitations,
which are discussed in the manual.
If a file contains interactive form fields and indicates that the
appearances are out of date with the values of the form, this flag
will regenerate appearances, subject to a few limitations. Note
that there is usually no reason to do this, but it can be
necessary before using the :qpdf:ref:`--flatten-annotations`
option. Here is a summary of the limitations.
- Radio button and checkbox appearances use the pre-set values in
the PDF file. :command:`qpdf` just makes sure that the correct
appearance is displayed based on the value of the field. This is
fine for PDF files that create their forms properly. Some PDF
writers save appearances for fields when they change, which could
cause some controls to have inconsistent appearances.
- For text fields and list boxes, any characters that fall outside
of US-ASCII or, if detected, "Windows ANSI" or "Mac Roman"
encoding, will be replaced by the ``?`` character.
:command:`qpdf` does not know enough about fonts and encodings to
correctly represent characters that fall outside of this range.
- Quadding is ignored. Quadding is used to specify whether the
contents of a field should be left, center, or right aligned with
the field.
- Rich text, multi-line, and other more elaborate formatting
directives are ignored.
- There is no support for multi-select fields or signature fields.
Appearances generated by :command:`qpdf` should be good enough for
simple forms consisting of ASCII characters where the original file
followed the PDF specification and provided template information
for text field appearances. If :command:`qpdf` doesn't do a good
enough job with your form, use an external application to save your
filled-in form before processing it with :command:`qpdf`. Most PDF
viewers that support filling in of forms will generate appearance
streams. Some of them will even do it for forms filled in with
characters outside the original font's character range by embedding
additional fonts as needed.
.. qpdf:option:: --optimize-images
.. help: use efficient compression for images
Attempt to use DCT (JPEG) compression for images that fall
within certain constraints as long as doing so decreases the
size in bytes of the image. See also help for the following
options:
--oi-min-width
--oi-min-height
--oi-min-area
--keep-inline-images
This flag causes qpdf to recompress all images that are not
compressed with DCT (JPEG) using DCT compression as long as doing
so decreases the size in bytes of the image data and the image does
not fall below minimum specified dimensions. Useful information is
provided when used in combination with :qpdf:ref:`--verbose`. See
also the :qpdf:ref:`--oi-min-width`, :qpdf:ref:`--oi-min-height`,
and :qpdf:ref:`--oi-min-area` options. By default, inline images
are converted to regular images and optimized as well. Use
:qpdf:ref:`--keep-inline-images` to prevent inline images from
being included.
.. qpdf:option:: --oi-min-width=width
.. help: minimum width for --optimize-images
Don't optimize images whose width is below the specified value.
Avoid optimizing images whose width is below the specified amount. If
omitted, the default is 128 pixels. Use 0 for no minimum.
.. qpdf:option:: --oi-min-height=height
.. help: minimum height for --optimize-images
Don't optimize images whose height is below the specified value.
Avoid optimizing images whose height is below the specified amount.
If omitted, the default is 128 pixels. Use 0 for no minimum.
.. qpdf:option:: --oi-min-area=area-in-pixels
.. help: minimum area for --optimize-images
Don't optimize images whose area in pixels is below the specified value.
Avoid optimizing images whose pixel count
(:samp:`{width}` × :samp:`{height}`) is below the specified amount.
If omitted, the default is 16,384 pixels. Use 0 for no minimum.
.. qpdf:option:: --keep-inline-images
.. help: exclude inline images from optimization
Prevent inline images from being considered by --optimize-images.
Prevent inline images from being included in image optimization
done by :qpdf:ref:`--optimize-images`.
.. qpdf:option:: --remove-page-labels
.. help: remove explicit page numbers
Exclude page labels (explicit page numbers) from the output file.
Exclude page labels (explicit page numbers) from the output file.
.. _encryption-options:
Encryption
----------
.. help-topic encryption: create encrypted files
Create encrypted files. Usage:
--encrypt user-password owner-password key-length [options] --
Either or both of user-password and owner-password may be empty
strings. key-length may be 40, 128, or 256. Encryption options are
terminated by "--" by itself.
40-bit encryption is insecure, as is 128-bit encryption without
AES. Use 256-bit encryption unless you have a specific reason to
use an insecure format, such as testing or compatibility with very
old viewers. You must use the --allow-weak-crypto to create
encrypted files that use insecure cryptographic algorithms. The
--allow-weak-crypto flag appears outside of --encrypt ... --
(before --encrypt or after --).
Available options vary by key length. Not all readers respect all
restrictions. Different PDF readers respond differently to various
combinations of options. Sometimes a PDF viewer may show you
restrictions that differ from what you selected. This is probably
not a bug in qpdf.
Options for 40-bit only:
--annotate=[y|n] restrict comments, filling forms, and signing
--extract=[y|n] restrict text/graphic extraction
--modify=[y|n] restrict document modification
--print=[y|n] restrict printing
Options for 128-bit or 256-bit:
--accessibility=[y|n] restrict accessibility (usually ignored)
--annotate=[y|n] restrict commenting/filling form fields
--assemble=[y|n] restrict document assembly
--extract=[y|n] restrict text/graphic extraction
--form=[y|n] restrict filling form fields
--modify-other=[y|n] restrict other modifications
--modify=modify-opt control modify access by level
--print=print-opt control printing access
--cleartext-metadata prevent encryption of metadata
For 128-bit only:
--use-aes=[y|n] indicates whether to use AES encryption
--force-V4 forces use of V=4 encryption handler
For 256-bit only:
--force-R5 forces use of deprecated R=5 encryption
--allow-insecure allow user password with empty owner password
Values for print-opt:
none disallow printing
low allow only low-resolution printing
full allow full printing
Values for modify-opt:
none allow no modifications
assembly allow document assembly only
form assembly + filling in form fields and signing
annotate form + commenting and modifying forms
all allow full document modification
This section describes the options used to create encrypted files. For
other options related to encryption, see also :qpdf:ref:`--decrypt`
and :qpdf:ref:`--copy-encryption`. For a more in-depth technical
discussion of how PDF encryption works internally, see
:ref:`pdf-encryption`.
To create an encrypted file, use
::
--encrypt user-password owner-password key-length [options] --
Either or both of :samp:`{user-password}` and :samp:`{owner-password}`
may be empty strings. :samp:`{key-length}` may be ``40``, ``128``, or
``256``. Encryption options are terminated by ``--`` by itself.
40-bit encryption is insecure, as is 128-bit encryption without AES.
Use 256-bit encryption unless you have a specific reason to use an
insecure format, such as testing or compatibility with very old
viewers. You must use the :qpdf:ref:`--allow-weak-crypto` flag to
create encrypted files that use insecure cryptographic algorithms. The
:qpdf:ref:`--allow-weak-crypto` flag appears outside of ``--encrypt
... --`` (before ``--encrypt`` or after ``--``).
If :samp:`{key-length}` is 256, the minimum PDF version is 1.7 with
extension level 8, and the AES-based encryption format used is the one
described in the PDF 2.0 specification. Using 128-bit encryption
forces the PDF version to be at least 1.4, or if AES is used, 1.6.
Using 40-bit encryption forces the PDF version to be at least 1.3.
When 256-bit encryption is used, PDF files with empty owner
passwords are insecure. To create such files, you must specify the
:qpdf:ref:`--allow-insecure` option.
Available options vary by key length. Not all readers respect all
restrictions. The default for each permission option is to be fully
permissive. These restrictions may or may not be enforced by any
particular reader. :command:`qpdf` allows very granular setting of
restrictions. Some readers may not recognize the combination of
options you specify. If you specify certain combinations of
restrictions and find a reader that doesn't seem to honor them as you
expect, it is most likely not a bug in :command:`qpdf`. qpdf itself
does not obey encryption restrictions already imposed on the file.
Doing so would be meaningless since qpdf can be used to remove
encryption from the file entirely.
Here is a summary of encryption options. Details are provided in the
help for each option.
.. list-table:: Options for 40-bit Encryption Only
:widths: 30 70
:header-rows: 0
- - ``--annotate=[y|n]``
- restrict comments, filling forms, and signing
- - ``--extract=[y|n]``
- restrict text/graphic extraction
- - ``--modify=[y|n]``
- restrict document modification
- - ``--print=[y|n]``
- restrict printing
.. list-table:: Options for 128-bit or 256-bit Encryption
:widths: 30 70
:header-rows: 0
- - ``--accessibility=[y|n]``
- restrict accessibility (usually ignored)
- - ``--annotate=[y|n]``
- restrict commenting/filling form fields
- - ``--assemble=[y|n]``
- restrict document assembly
- - ``--extract=[y|n]``
- restrict text/graphic extraction
- - ``--form=[y|n]``
- restrict filling form fields
- - ``--modify-other=[y|n]``
- restrict other modifications
- - ``--modify=modify-opt``
- control modify access by level
- - ``--print=print-opt``
- control printing access
- - ``--cleartext-metadata``
- prevent encryption of metadata
.. list-table:: Options for 128-bit Encryption Only
:widths: 35 65
:header-rows: 0
- - ``--use-aes=[y|n]``
- indicates whether to use AES encryption
- - ``--force-V4``
- forces use of V=4 encryption handler
.. list-table:: Options for 256-bit Encryption Only
:widths: 30 70
:header-rows: 0
- - ``--force-R5``
- forces use of deprecated ``R=5`` encryption algorithm
- - ``--allow-insecure``
- allow user password with empty owner password
.. list-table:: Values for :samp:`{print-opt}`
:widths: 20 80
:header-rows: 0
- - ``none``
- disallow printing
- - ``low``
- allow only low-resolution printing
- - ``full``
- allow full printing
.. list-table:: Values for :samp:`{modify-opt}`
:widths: 20 80
:header-rows: 0
- - ``none``
- allow no modifications
- - ``assembly``
- allow document assembly only
- - ``form``
- ``assembly`` permissions plus filling in form fields and
signing
- - ``annotate``
- ``form`` permissions plus commenting and modifying forms
- - ``all``
- allow full document modification
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --accessibility=[y|n]
.. help: restrict document accessibility
This option is ignored except with very old encryption formats.
The current PDF specification does not allow restriction of
document accessibility. This option is not available with 40-bit
encryption.
Enable/disable extraction of text for accessibility to visually
impaired users. The default is to be fully permissive. The qpdf
library disregards this field when AES is used with 128-bit
encryption or when 256-bit encryption is used. You should never
disable accessibility unless you are explicitly doing so for
creating test files. The PDF spec says that conforming readers
should disregard this permission and always allow accessibility.
This option is not available with 40-bit encryption.
.. qpdf:option:: --annotate=[y|n]
.. help: restrict document annotation
Enable/disable modifying annotations including making comments
and filling in form fields. For 128-bit and 256-bit encryption,
this also enables editing, creating, and deleting form fields
unless --modify-other=n or --modify=none is also specified.
Enable/disable modifying annotations including making comments and
filling in form fields. The default is to be fully permissive. For
128-bit and 256-bit encryption, this also enables editing,
creating, and deleting form fields unless :samp:`--modify-other=n`
or :samp:`--modify=none` is also specified.
.. qpdf:option:: --assemble=[y|n]
.. help: restrict document assembly
Enable/disable document assembly (rotation and reordering of
pages). This option is not available with 40-bit encryption.
Enable/disable document assembly (rotation and reordering of
pages). The default is to be fully permissive.
This option is not available with 40-bit encryption.
.. qpdf:option:: --extract=[y|n]
.. help: restrict text/graphic extraction
Enable/disable text/graphic extraction for purposes other than
accessibility.
Enable/disable text/graphic extraction for purposes other than
accessibility. The default is to be fully permissive.
.. qpdf:option:: --form=[y|n]
.. help: restrict form filling
Enable/disable whether filling form fields is allowed even if
modification of annotations is disabled. This option is not
available with 40-bit encryption.
Enable/disable whether filling form fields is allowed even if
modification of annotations is disabled. The default is to be fully
permissive.
This option is not available with 40-bit encryption.
.. qpdf:option:: --modify-other=[y|n]
.. help: restrict other modifications
Enable/disable modifications not controlled by --assemble,
--annotate, or --form. --modify-other=n is implied by any of the
other --modify options. This option is not available with 40-bit
encryption.
Enable/disable modifications not controlled by
:qpdf:ref:`--assemble`, :qpdf:ref:`--annotate`, or
:qpdf:ref:`--form`. ``--modify-other=n`` is implied by any of the
other :qpdf:ref:`--modify` options except for ``--modify=all``. The
default is to be fully permissive.
This option is not available with 40-bit encryption.
.. qpdf:option:: --modify=modify-opt
.. help: restrict document modification
For 40-bit files, modify-opt may only be y or n and controls all
aspects of document modification.
For 128-bit and 256-bit encryption, modify-opt values allow
enabling and disabling levels of restriction in a manner similar
to how some PDF creation tools do it. modify-opt values map to
other combinations of options as follows:
all: allow full modification (the default)
annotate: --modify-other=n
form: --modify-other=n --annotate=n
assembly: --modify-other=n --annotate=n --form=n
none: --modify-other=n --annotate=n --form=n --assemble=n
For 40-bit files, :samp:`{modify-opt}` may only be ``y`` or ``n``
and controls all aspects of document modification. The default is
to be fully permissive.
For 128-bit and 256-bit encryption, :samp:`{modify-opt}` values
allow enabling and disabling levels of restriction in a manner
similar to how some PDF creation tools do it:
.. list-table:: :samp:`{modify-opt}` for 128-bit and 256-bit Encryption
:widths: 10 80
:header-rows: 0
- - ``none``
- allow no modifications
- - ``assembly``
- allow document assembly only
- - ``form``
- ``assembly`` permissions plus filling in form fields and
signing
- - ``annotate``
- ``form`` permissions plus commenting and modifying forms
- - ``all``
- allow full document modification (the default)
Modify options correspond to the more granular options as follows:
.. list-table:: Mapping :samp:`{modify-opt}` to Other Options
:widths: 10 80
:header-rows: 0
- - ``none``
- ``--modify-other=n --annotate=n --form=n --assemble=n``
- - ``assembly``
- ``--modify-other=n --annotate=n --form=n``
- - ``form``
- ``--modify-other=n --annotate=n``
- - ``annotate``
- ``--modify-other=n``
- - ``all``
- no other modify options (the default)
You can combine this option with the options listed above. If you
do, later options override earlier options.
.. qpdf:option:: --print=print-opt
.. help: restrict printing
Control what kind of printing is allowed. For 40-bit encryption,
print-opt may only be y or n and enables or disables all
printing. For 128-bit and 256-bit encryption, print-opt may have
the following values:
none: disallow printing
low: allow low-resolution printing only
full: allow full printing (the default)
Control what kind of printing is allowed. The default is to be
fully permissive. For 40-bit encryption, :samp:`{print-opt}` may
only be ``y`` or ``n`` and enables or disables all printing. For
128-bit and 256-bit encryption, :samp:`{print-opt}` may have the
following values:
.. list-table:: :samp:`{print-opt}` Values
:widths: 10 80
:header-rows: 0
- - :samp:`none`
- disallow printing
- - :samp:`low`
- allow low-resolution printing only
- - :samp:`full`
- allow full printing (the default)
.. qpdf:option:: --cleartext-metadata
.. help: don't encrypt metadata
If specified, don't encrypt document metadata even when
encrypting the rest of the document. This option is not
available with 40-bit encryption.
If specified, any metadata stream in the document will be left
unencrypted even if the rest of the document is encrypted. This also
forces the PDF version to be at least 1.5.
This option is not available with 40-bit encryption.
.. qpdf:option:: --use-aes=[y|n]
.. help: use AES with 128-bit encryption
Enables/disables use of the more secure AES encryption with
128-bit encryption. Specifying --use-aes=y forces the PDF
version to be at least 1.6. This option is only available with
128-bit encryption. The default is "n" for compatibility
reasons. Use 256-bit encryption instead.
Enables/disables use of the more secure AES encryption with 128-bit
encryption. Specifying ``--use-aes=y`` forces the PDF version to be
at least 1.6. This option is only available with 128-bit
encryption. The default is ``n`` for compatibility reasons. Use
256-bit encryption instead.
.. qpdf:option:: --allow-insecure
.. help: allow empty owner passwords
Allow creation of PDF files with empty owner passwords and
non-empty user passwords when using 256-bit encryption.
Allow creation of PDF files with 256-bit keys where the user
password is non-empty and the owner password is empty. Files
created in this way are insecure since they can be opened without a
password, and restrictions will not be enforced. Users would
ordinarily never want to create such files. If you are using qpdf
to intentionally created strange files for testing (a valid use of
qpdf!), this option allows you to create such insecure files. This
option is only available with 256-bit encryption.
See :ref:`pdf-passwords` for a more technical discussion of this
issue.
.. qpdf:option:: --force-V4
.. help: force V=4 in encryption dictionary
This option is for testing and is never needed in practice since
qpdf does this automatically when needed.
Use of this option forces the ``V`` and ``R`` parameters in the
document's encryption dictionary to be set to the value ``4``. As
qpdf will automatically do this when required, there is no reason
to ever use this option. It exists primarily for use in testing
qpdf itself. This option also forces the PDF version to be at least
1.5.
.. qpdf:option:: --force-R5
.. help: use unsupported R=5 encryption
Use an undocumented, unsupported, deprecated encryption
algorithm that existed only in Acrobat version IX. This option
should not be used except for compatibility testing.
Use an undocumented, unsupported, deprecated encryption algorithm
that existed only in Acrobat version IX. This option should not be
used except for compatibility testing. If specified, qpdf sets the
minimum version to 1.7 at extension level 3.
.. _page-selection:
Page Selection
--------------
.. help-topic page-selection: select pages from one or more files
Use the --pages option to select pages from multiple files. Usage:
qpdf in.pdf --pages input-file [--password=password] [page-range] \
[...] -- out.pdf
Between --pages and the -- that terminates pages option, repeat
the following:
filename [--password=password] [page-range]
Document-level information, such as outlines, tags, etc., is taken
from in.pdf and is preserved in out.pdf. You can use --empty in place
of an input file to start from an empty file and just copy pages
equally from all files. You can use "." as a shorthand for the
primary input file (if not --empty). In the above example, "."
would refer to in.pdf.
Use --password=password to specify the password for a
password-protected input file. If the same input file is used more
than once, you only need to supply the password the first time. If
the page range is omitted, all pages are selected.
Run qpdf --help=page-ranges for help with page ranges.
Use --collate=n to cause pages to be collated in groups of n pages
(default 1) instead of concatenating the input.
Examples:
- Start with in.pdf and append all pages from a.pdf and the even
pages from b.pdf, and write the output to out.pdf. Document-level
information from in.pdf is retained. Note the use of "." to refer
to in.pdf.
qpdf in.pdf --pages . a.pdf b.pdf:even -- out.pdf
- Take all the pages from a.pdf, all the pages from b.pdf in
reverse, and only pages 3 and 6 from c.pdf and write the result
to out.pdf. Use password "x" to open b.pdf:
qpdf --empty --pages a.pdf b.pdf --password=x z-1 c.pdf 3,6
More examples are in the manual.
:command:`qpdf` allows you to use the :qpdf:ref:`--pages` option to
split and merge PDF files by selecting pages from one or more input
files.
Usage: :samp:`qpdf {in.pdf} --pages input-file [--password={password}] [{page-range}] [...] -- {out.pdf}`
Between ``--pages`` and the ``--`` that terminates pages option,
repeat the following:
:samp:`{filename} [--password={password}] [{page-range}]`
Notes:
- The password option is needed only for password-protected files.
If you specify the same file more than once, you only need to supply
the password the first time.
- The page range may be omitted. If omitted, all pages are included.
- Document-level information, such as outlines, tags, etc., is taken
from the primary input file (in the above example, :file:`in.pdf`)
and is preserved in :file:`out.pdf`. You can use
:qpdf:ref:`--empty` in place of an input file to start from an
empty file and just copy pages equally from all files.
- You can use ``.`` as a shorthand for the primary input file, if not
empty.
See :ref:`page-ranges` for help on specifying a page range.
Use :samp:`--collate={n}` to cause pages to be collated in groups of
:samp:`{n}` pages (default 1) instead of concatenating the input. Note
that the :qpdf:ref:`--collate` appears outside of ``--pages ... --``
(before ``--pages`` or after ``--``). Pages are pulled from each
document in turn. When a document is out of pages, it is skipped. See
examples below.
Examples
~~~~~~~~
- Start with :file:`in.pdf` and append all pages from :file:`a.pdf`
and the even pages from :file:`b.pdf`, and write the output to
:file:`out.pdf`. Document-level information from :file:`in.pdf` is
retained. Note the use of ``.`` to refer to :file:`in.pdf`.
::
qpdf in.pdf --pages . a.pdf b.pdf:even -- out.pdf
- Take all the pages from :file:`a.pdf`, all the pages from
:file:`b.pdf` in reverse, and only pages 3 and 6 from :file:`c.pdf`
and write the result to :file:`out.pdf`. Document-level metadata is
discarded from all input files. The password ``x`` is used to open
:file:`b.pdf`.
::
qpdf --empty --pages a.pdf b.pdf --password=x z-1 c.pdf 3,6
- Scan a document with double-sided printing by scanning the fronts
into :file:`odd.pdf` and the backs into :file:`even.pdf`. Collate
the results into :file:`all.pdf`. This takes the first page of
:file:`odd.pdf`, the first page of :file:`even.pdf`, the second page
of :file:`odd.pdf`, the second page of :file:`even.pdf`, etc.
::
qpdf --collate odd.pdf --pages . even.pdf -- all.pdf
OR
qpdf --collate --empty --pages odd.pdf even.pdf -- all.pdf
- When collating, any number of files and page ranges can be
specified. If any file has fewer pages, that file is just skipped
when its pages have all been included. For example, if you ran
::
qpdf --collate --empty --pages a.pdf 1-5 b.pdf 6-4 c.pdf r1 -- out.pdf
you would get the following pages in this order:
- a.pdf page 1
- b.pdf page 6
- c.pdf last page
- a.pdf page 2
- b.pdf page 5
- a.pdf page 3
- b.pdf page 4
- a.pdf page 4
- a.pdf page 5
- You can specify a numeric parameter to :qpdf:ref:`--collate`. With
:samp:`--collate={n}`, pull groups of :samp:`{n}` pages from each
file, as always, stopping when there are no more pages. For example,
if you ran
::
qpdf --collate=2 --empty --pages a.pdf 1-5 b.pdf 6-4 c.pdf r1 -- out.pdf
you would get the following pages in this order:
- a.pdf page 1
- a.pdf page 2
- b.pdf page 6
- b.pdf page 5
- c.pdf last page
- a.pdf page 3
- a.pdf page 4
- b.pdf page 4
- a.pdf page 5
- Take pages 1 through 5 from :file:`file1.pdf` and pages 11 through
15 in reverse from :file:`file2.pdf`, taking document-level metadata
from :file:`file2.pdf`.
::
qpdf file2.pdf --pages file1.pdf 1-5 . 15-11 -- outfile.pdf
- Here's a more contrived example. If, for some reason, you wanted to
take the first page of an encrypted file called
:file:`encrypted.pdf` with password ``pass`` and repeat it twice in
an output file without any shared data between the two copies of
page 1, and if you wanted to drop document-level metadata but
preserve encryption, you could run
::
qpdf --empty --copy-encryption=encrypted.pdf \
--encryption-file-password=pass \
--pages encrypted.pdf --password=pass 1 \
./encrypted.pdf --password=pass 1 -- \
outfile.pdf
Note that we had to specify the password all three times because
giving a password as :qpdf:ref:`--encryption-file-password` doesn't
count for page selection, and as far as qpdf is concerned,
:file:`encrypted.pdf` and :file:`./encrypted.pdf` are separate
files. (This is by design. See :ref:`page-limitations` for a
discussion.) These are all corner cases that most users should
hopefully never have to be bothered with.
.. _page-limitations:
Limitations
~~~~~~~~~~~
With the exception of page labels (page numbers), :command:`qpdf`
doesn't yet have full support for handling document-level data as it
relates to pages. Certain document-level features such as form fields,
outlines (bookmarks), and article tags among others, are copied in
their entirety from the primary input file. Starting with qpdf version
8.3, page labels are preserved from all files unless
:qpdf:ref:`--remove-page-labels` is specified.
.. If updating this after limitations are removed or reduced,
recheck --split-pages as well.
It is expected that a future version of :command:`qpdf` will have more
complete and configurable behavior regarding document-level metadata.
In the meantime, semantics of splitting and merging vary across
features. For example, the document's outlines (bookmarks) point to
actual page objects, so if you select some pages and not others,
bookmarks that point to pages that are in the output file will work,
and remaining bookmarks will not work. If you don't want to preserve
the primary file's metadata, use :qpdf:ref:`--empty` as the primary
input file.
Visit `qpdf issues labeled with "pages"
<https://github.com/qpdf/qpdf/issues?q=is%3Aopen+is%3Aissue+label%3Apages>`__
or look at the :file:`TODO` file in the qpdf source distribution for
some of the ideas.
.. NOTE:
The workaround described in the following paragraph is mentioned in
the documentation in more than one place. Searching for ./ should
help find them. It is also in the test suite. I believe there are
several valid uses cases for doing this, and so it is my intention
to leave the behavior of treating different paths to the same file
as separate even if the above limitations are removed. See also
https://github.com/qpdf/qpdf/issues/399
Prior to :command:`qpdf` version 8.4, it was not possible to specify
the same page from the same file directly more than once, and a
workaround of specifying the same file in more than one way was
required. Version 8.4 removes this limitation, but when the same page
is copied more than once, all its data is shared between the pages.
Sometimes this is fine, but sometimes it may not work correctly,
particularly if there are form fields or you intend to perform other
modifications on one of the pages. A future version of qpdf should
address this more completely. You can work around this by specifying
the same file in two different ways. For example :command:`qpdf
in.pdf --pages . 1 ./in.pdf 1 -- out.pdf` would create a file with two
copies of the first page of the input, and the two copies would not
share any objects in common. This includes fonts, images, and anything
else the page references.
.. _overlay-underlay:
Overlay and Underlay
--------------------
.. help-topic overlay-underlay: overlay/underlay pages from other files
These options allow pages from another file to be overlaid or
underlaid on the primary output. Overlaid pages are drawn on top of
the destination page and may obscure the page. Underlaid pages are
drawn below the destination page. Usage:
{--overlay|--underlay} file
[--password=password]
[--to=page-range]
[--from=[page-range]]
[--repeat=page-range]
--
Note the use of "--" by itself to terminate overlay/underlay options.
For overlay and underlay, a file and optional password are specified, along
with a series of optional page ranges. The default behavior is that each
page of the overlay or underlay file is imposed on the corresponding page
of the primary output until it runs out of pages, and any extra pages are
ignored. You can also give a page range with --repeat to cause
those pages to be repeated after the original pages are exhausted.
Run qpdf --help=page-ranges for help with page ranges.
You can use :command:`qpdf` to overlay or underlay pages from other
files onto the output generated by qpdf. Specify overlay or underlay
as follows:
::
{--overlay|--underlay} file [options] --
Overlay and underlay options are processed late, so they can be
combined with other options like merging and will apply to the final
output. The ``--overlay`` and ``--underlay`` options work the same
way, except underlay pages are drawn underneath the page to which they
are applied, possibly obscured by the original page, and overlay files
are drawn on top of the page to which they are applied, possibly
obscuring the page. You can combine overlay and underlay, but you can
only specify each option at most one time.
The default behavior of overlay and underlay is that pages are taken
from the overlay/underlay file in sequence and applied to
corresponding pages in the output until there are no more output
pages. If the overlay or underlay file runs out of pages, remaining
output pages are left alone. This behavior can be modified by options,
which are provided between the ``--overlay`` or ``--underlay`` flag
and the ``--`` option. The following options are supported:
.. qpdf:option:: --to=page-range
.. help: destination pages for underlay/overlay
Specify the range of pages in the primary output to apply
overlay/underlay to. See qpdf --help=page-ranges for help with
the page range syntax.
Specify a page range (see :ref:`page-ranges`) that indicates which
pages in the output should have the overlay/underlay applied. If not
specified, overlay/underlay are applied to all pages.
.. qpdf:option:: --from=[page-range]
.. help: source pages for underlay/overlay
Specify pages from the overlay/underlay file that are applied to
the destination pages. See qpdf --help=page-ranges for help
with the page range syntax. The page range may be omitted
if --repeat is used.
Specify a page range that indicates which pages in the
overlay/underlay file will be used for overlay or underlay. If not
specified, all pages will be used. The "from" pages are used until
they are exhausted, after which any pages specified with
:qpdf:ref:`--repeat` are used. If you are using the
:qpdf:ref:`--repeat` option, you can use ``--from=`` to provide an
empty set of "from" pages.
This Can be left empty by omitting
:samp:`{page-range}`
.. qpdf:option:: --repeat=page-range
.. help: overlay/underlay pages to repeat
Specify pages from the overlay/underlay that are repeated after
"from" pages have been exhausted. See qpdf --help=page-ranges
for help with the page range syntax.
Specify an optional page range that indicates which pages in the
overlay/underlay file will be repeated after the "from" pages are used
up. If you want to apply a repeat a range of pages starting with the
first page of output, you can explicitly use ``--from=``.
Examples
~~~~~~~~
- Overlay the first three pages from file :file:`o.pdf` onto the first
three pages of the output, then overlay page 4 from :file:`o.pdf`
onto pages 4 and 5 of the output. Leave remaining output pages
untouched.
::
qpdf in.pdf --overlay o.pdf --to=1-5 --from=1-3 --repeat=4 -- out.pdf
- Underlay page 1 of :file:`footer.pdf` on all odd output pages, and
underlay page 2 of :file:`footer.pdf` on all even output pages.
::
qpdf in.pdf --underlay footer.pdf --from= --repeat=1,2 -- out.pdf
- Combine two files and overlay the single page from watermark.pdf on
the result.
::
qpdf --empty --pages a.pdf b.pdf -- \
--overlay watermark.pdf --from= --repeat=1 -- out.pdf
.. _attachments:
Embedded Files/Attachments
--------------------------
.. help-topic attachments: work with embedded files
It is possible to list, add, or delete embedded files (also known
as attachments) and to copy attachments from other files. See help
on individual options for details. Run qpdf --help=add-attachment
for additional details about adding attachments. See also
--help=--list-attachments and --help=--show-attachment.
It is possible to list, add, or delete embedded files (also known as
attachments) and to copy attachments from other files. See also
:qpdf:ref:`--list-attachments` and :qpdf:ref:`--show-attachment`.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --add-attachment file [options] --
.. help: start add attachment options
The --add-attachment flag and its options may be repeated to add
multiple attachments. Run qpdf --help=add-attachment for details.
This flag starts add attachment options, which are used to add
attachments to a file.
The ``--add-attachment`` flag and its options may be repeated to
add multiple attachments. Please see :ref:`add-attachment` for
additional details.
.. qpdf:option:: --copy-attachments-from file [options] --
.. help: start copy attachment options
The --copy-attachments-from flag and its options may be repeated
to copy attachments from multiple files. Run
qpdf --help=copy-attachments for details.
This flag starts copy attachment options, which are used to copy
attachments from other files.
The ``--copy-attachments-from`` flag and its options may be
repeated to copy attachments from multiple files. Please see
:ref:`copy-attachments` for additional details.
.. qpdf:option:: --remove-attachment=key
.. help: remove an embedded file
Remove an embedded file using its key. Get the key with
--list-attachments.
Remove the specified attachment. This doesn't only remove the
attachment from the embedded files table but also clears out the
file specification to ensure that the attachment is actually not
present in the output file. That means that any potential internal
links to the attachment will be broken. Run with :qpdf:ref:`--verbose` to
see status of the removal. Use :qpdf:ref:`--list-attachments` to find
the attachment key. This option may be repeated to remove multiple
attachments.
.. _pdf-dates:
PDF Date Format
~~~~~~~~~~~~~~~
.. help-topic pdf-dates: PDF date format
When a date is required, the date should conform to the PDF date
format specification, which is "D:yyyymmddhhmmssz" where "z" is
either literally upper case "Z" for UTC or a timezone offset in
the form "-hh'mm'" or "+hh'mm'". Negative timezone offsets indicate
time before UTC. Positive offsets indicate how far after. For
example, US Eastern Standard Time (America/New_York) is "-05'00'",
and Indian Standard Time (Asia/Calcutta) is "+05'30'".
Examples:
- D:20210207161528-05'00' February 7, 2021 at 4:15:28 p.m.
- D:20210207211528Z February 7, 2021 at 21:15:28 UTC
When a date is required, the date should conform to the PDF date
format specification, which is :samp:`D:{yyyymmddhhmmssz}` where
:samp:`{z}` is either literally upper case ``Z`` for UTC or a
timezone offset in the form :samp:`{-hh'mm'}` or :samp:`{+hh'mm'}`.
Negative timezone offsets indicate time before UTC. Positive offsets
indicate how far after. For example, US Eastern Standard Time
(America/New_York) is ``-05'00'``, and Indian Standard Time
(Asia/Calcutta) is ``+05'30'``.
.. list-table:: PDF Date Examples
:widths: 30 70
:header-rows: 0
- - ``D:20210207161528-05'00'``
- February 7, 2021 at 4:15:28 p.m.
- - ``D:20210207211528Z``
- February 7, 2021 at 21:15:28 UTC
.. _add-attachment:
Options for Adding Attachments
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. help-topic add-attachment: attach (embed) files
The options listed below appear between --add-attachment and its
terminating "--".
These options are valid between :qpdf:ref:`--add-attachment` and ``--``.
.. qpdf:option:: --key=key
.. help: specify attachment key
Specify the key to use for the attachment in the embedded files
table. It defaults to the last element (basename) of the
attached file's filename.
Specify the key to use for the attachment in the embedded files
table. It defaults to the last element of the attached file's
filename. For example, if you say ``--add-attachment
/home/user/image.png``, the default key will be just ``image.png``.
.. qpdf:option:: --filename=name
.. help: set attachment's displayed filename
Specify the filename to be used for the attachment. This is what
is usually displayed to the user and is the name most graphical
PDF viewers will use when saving a file. It defaults to the last
element (basename) of the attached file's filename.
Specify the filename to be used for the attachment. This is what is
usually displayed to the user and is the name most graphical PDF
viewers will use when saving a file. It defaults to the last
element of the attached file's filename. For example, if you say
``--add-attachment /home/user/image.png``, the default key will be
just ``image.png``.
.. qpdf:option:: --creationdate=date
.. help: set attachment's creation date
Specify the attachment's creation date in PDF format; defaults
to the current time. Run qpdf --help=pdf-dates for information
about the date format.
Specify the attachment's creation date in PDF format; defaults to
the current time. See :ref:`pdf-dates` for information about the
date format.
.. qpdf:option:: --moddate=date
.. help: set attachment's modification date
Specify the attachment's modification date in PDF format;
defaults to the current time. Run qpdf --help=pdf-dates for
information about the date format.
Specify the attachment's modification date in PDF format; defaults
to the current time. See :ref:`pdf-dates` for information about the
date format.
.. qpdf:option:: --mimetype=type/subtype
.. help: attachment mime type, e.g. application/pdf
Specify the mime type for the attachment, such as text/plain,
application/pdf, image/png, etc.
Specify the mime type for the attachment, such as ``text/plain``,
``application/pdf``, ``image/png``, etc. The qpdf library does not
automatically determine the mime type. In a UNIX-like environment,
the :command:`file` command can often provide this information. In
MacOS, you can use :samp:`file -I {filename}`. In Linux, it's
:samp:`file -i {filename}`.
Implementation note: the mime type appears in a field called
``/Subtype`` in the PDF file, but that field actually includes the
full type and subtype of the mime type. This is because ``/Type``
already means something else in PDF.
.. qpdf:option:: --description="text"
.. help: set attachment's description
Supply descriptive text for the attachment, displayed by some
PDF viewers.
Supply descriptive text for the attachment, displayed by some PDF
viewers.
.. qpdf:option:: --replace
.. help: replace attachment with same key
Indicate that any existing attachment with the same key should
be replaced by the new attachment. Otherwise, qpdf gives an
error if an attachment with that key is already present.
Indicate that any existing attachment with the same key should be
replaced by the new attachment. Otherwise, :command:`qpdf` gives an
error if an attachment with that key is already present.
.. _copy-attachments:
Options for Copying Attachments
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. help-topic copy-attachments: copy attachments from another file
The options listed below appear between --copy-attachments-from and
its terminating "--".
To copy attachments from a password-protected file, use
the --password option after the file name.
Options in this section are valid between
:qpdf:ref:`--copy-attachments-from` and ``--``.
.. qpdf:option:: --prefix=prefix
.. help: key prefix for copying attachments
Prepend a prefix to each key; may be needed if there are
duplicate attachment keys. This affects the key only, not the
file name.
Only required if the file from which attachments are being copied
has attachments with keys that conflict with attachments already
in the file. In this case, the specified prefix will be prepended
to each key. This affects only the key in the embedded files
table, not the file name. The PDF specification doesn't preclude
multiple attachments having the same file name.
.. _inspection-options:
PDF Inspection
--------------
.. help-topic inspection: inspect PDF files
These options provide tools for inspecting PDF files. When any of
the options in this section are specified, no output file may be
given.
These options provide tools for inspecting PDF files. When any of the
options in this section are specified, no output file may be given.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --is-encrypted
.. help: silently test whether a file is encrypted
Silently exit with a code indicating the file's encryption status:
0: the file is encrypted
1: not used
2: the file is not encrypted
This can be used with password-protected files even if you don't
know the password.
Silently exit with a code indicating the file's encryption status:
.. list-table:: Exit Codes for ``--is-encrypted``
:widths: 5 80
:header-rows: 0
- - ``0``
- the file is encrypted
- - ``1``
- not used
- - ``2``
- the file is not encrypted
This option can be used for password-protected files even if you
don't know the password.
This option is useful for shell scripts. Other options are ignored
if this is given. This option is mutually exclusive with
:qpdf:ref:`--requires-password`. Both this option and
:qpdf:ref:`--requires-password` exit with status ``2`` for
non-encrypted files.
.. qpdf:option:: --requires-password
.. help: silently test a file's password
Silently exit with a code indicating the file's password status:
0: a password, other than as supplied, is required
1: not used
2: the file is not encrypted
3: the file is encrypted, and correct password (if any) has been supplied
Silently exit with a code indicating the file's password status:
.. list-table:: Exit Codes for ``--requires-password``
:widths: 5 80
:header-rows: 0
- - ``0``
- a password, other than as supplied, is required
- - ``1``
- not used
- - ``2``
- the file is not encrypted
- - ``3``
- the file is encrypted, and correct password (if any) has
been supplied
Use with the :qpdf:ref:`--password` option to specify the password
to test.
The choice of exit status ``0`` to mean that a password is required
is to enable code like
.. code-block:: bash
if [ qpdf --requires-password file.pdf ]; then
# prompt for password
fi
If a password is supplied with :qpdf:ref:`--password`, that
password is used to open the file just as with any normal
invocation of :command:`qpdf`. That means that using this option
with :qpdf:ref:`--password` can be used to check the correctness of
the password. In that case, an exit status of ``3`` means the file
works with the supplied password. This option is mutually exclusive
with :qpdf:ref:`--is-encrypted`. Both this option and
:qpdf:ref:`--is-encrypted` exit with status ``2`` for non-encrypted
files.
.. qpdf:option:: --check
.. help: partially check whether PDF is valid
Check the structure of the PDF file as well as a number of other
aspects of the file, and write information about the file to
standard output. Note that qpdf does not perform any validation
of the actual PDF page content or semantic correctness of the
PDF file. It merely checks that the PDF file is syntactically
valid. See also qpdf --help=exit-status.
Check the file's structure as well as encryption, linearization,
and encoding of stream data, and write information about the file
to standard output. An exit status of ``0`` indicates syntactic
correctness of the PDF file. Note that :samp:`--check` writes
nothing to standard error when everything is valid, so if you are
using this to programmatically validate files in bulk, it is safe
to run without output redirected to :file:`/dev/null` and just
check for a ``0`` exit code.
A file for which :samp:`--check` reports no errors may still have
errors in stream data content or may contain constructs that don't
conform to the PDF specification, but it should be syntactically
valid. If :samp:`--check` reports any errors, qpdf will exit with a
status of ``2``. There are some recoverable conditions that
:samp:`--check` detects. These are issued as warnings instead of
errors. If qpdf finds no errors but finds warnings, it will exit
with a status of ``3``. When :samp:`--check` is combined with other
options, checks are always performed before any other options are
processed. For erroneous files, :samp:`--check` will cause qpdf to
attempt to recover, after which other options are effectively
operating on the recovered file. Combining :samp:`--check` with
other options in this way can be useful for manually recovering
severely damaged files.
See also :ref:`exit-status`.
.. qpdf:option:: --show-encryption
.. help: information about encrypted files
Show document encryption parameters. Also show the document's
user password if the owner password is given and the file was
encrypted using older encryption formats that allow user
password recovery.
This option shows document encryption parameters. It also shows the
document's user password if the owner password is given and the
file was encrypted using older encryption formats that allow user
password recovery. (See :ref:`pdf-encryption` for a technical
discussion of this feature.) The output of ``--show-encryption`` is
included in the output of :qpdf:ref:`--check`.
.. qpdf:option:: --show-encryption-key
.. help: show key with --show-encryption
When used with --show-encryption or --check, causes the
underlying encryption key to be displayed.
When encryption information is being displayed, as when
:qpdf:ref:`--check` or :qpdf:ref:`--show-encryption` is given, display the
computed or retrieved encryption key as a hexadecimal string. This
value is not ordinarily useful to users, but it can be used as the
parameter to :qpdf:ref:`--password` if the :qpdf:ref:`--password-is-hex-key`
is specified. Note that, when PDF files are encrypted, passwords
and other metadata are used only to compute an encryption key, and
the encryption key is what is actually used for encryption. This
enables retrieval of that key. See :ref:`pdf-encryption` for a
technical discussion.
.. qpdf:option:: --check-linearization
.. help: check linearization tables
Check to see whether a file is linearized and, if so, whether
the linearization hint tables are correct.
Check to see whether a file is linearized and, if so, whether the
linearization hint tables are correct. qpdf does not check all
aspects of linearization. A linearized PDF file with linearization
errors that is otherwise correct is almost always readable by a PDF
viewer. As such, "errors" in PDF linearization are treated by
:command:`qpdf` as warnings.
.. qpdf:option:: --show-linearization
.. help: show linearization hint tables
Check and display all data in the linearization hint tables.
Check and display all data in the linearization hint tables.
.. qpdf:option:: --show-xref
.. help: show cross reference data
Show the contents of the cross-reference table or stream (object
locations in the file) in a human-readable form. This is
especially useful for files with cross-reference streams, which
are stored in a binary format.
Show the contents of the cross-reference table or stream in a
human-readable form. The cross-reference data gives the offset of
regular objects and the object stream ID and 0-based index within
the object stream for compressed objects. This is especially useful
for files with cross-reference streams, which are stored in a
binary format. If the file is invalid and cross reference table
reconstruction is performed, this option will show the information
in the reconstructed table.
.. qpdf:option:: --show-object={trailer|obj[,gen]}
.. help: show contents of an object
Show the contents of the given object. This is especially useful
for inspecting objects that are inside of object streams (also
known as "compressed objects").
Show the contents of the given object. This is especially useful
for inspecting objects that are inside of object streams (also
known as "compressed objects").
.. qpdf:option:: --raw-stream-data
.. help: show raw stream data
When used with --show-object, if the object is a stream, write
the raw (compressed) binary stream data to standard output
instead of the object's contents. See also
--filtered-stream-data.
When used with :qpdf:ref:`--show-object`, if the object is a
stream, write the raw (compressed) binary stream data to standard
output instead of the object's contents. Avoid combining this with
other inspection options to avoid commingling the stream data with
other output. See also :qpdf:ref:`--filtered-stream-data`.
.. qpdf:option:: --filtered-stream-data
.. help: show filtered stream data
When used with --show-object, if the object is a stream, write
the filtered (uncompressed, potentially binary) stream data to
standard output instead of the object's contents. See also
--raw-stream-data.
When used with :qpdf:ref:`--show-object`, if the object is a stream,
write the filtered (uncompressed, potentially binary) stream data
to standard output instead of the object's contents. If the stream
is filtered using filters that qpdf does not support, an error will
be issued. This option acts as if ``--decode-level=all`` was
specified (see :qpdf:ref:`--decode-level`), so it will uncompress
images compressed with supported lossy compression schemes. Avoid
combining this with other inspection options to avoid commingling
the stream data with other output.
This option may be combined with :qpdf:ref:`--normalize-content`.
If you do this, qpdf will attempt to run content normalization even
if the stream is not a content stream, which will probably produce
unusable results.
See also :qpdf:ref:`--raw-stream-data`.
.. qpdf:option:: --show-npages
.. help: show number of pages
Print the number of pages in the input file on a line by itself.
Useful for scripts.
Print the number of pages in the input file on a line by itself.
Since the number of pages appears by itself on a line, this option
can be useful for scripting if you need to know the number of pages
in a file.
.. qpdf:option:: --show-pages
.. help: display page dictionary information
Show the object and generation number for each page dictionary
object and for each content stream associated with the page.
Show the object and generation number for each page dictionary
object and for each content stream associated with the page. Having
this information makes it more convenient to inspect objects from a
particular page. See also :qpdf:ref:`--with-images`.
.. qpdf:option:: --with-images
.. help: include image details with --show-pages
When used with --show-pages, also shows the object and
generation numbers for the image objects on each page.
When used with :qpdf:ref:`--show-pages`, also shows the object and
generation numbers for the image objects on each page.
.. qpdf:option:: --list-attachments
.. help: list embedded files
Show the key and stream number for each embedded file. Combine
with --verbose for more detailed information.
Show the *key* and stream number for each embedded file. With
:qpdf:ref:`--verbose`, additional information, including preferred
file name, description, dates, and more are also displayed. The key
is usually but not always equal to the file name and is needed by
some of the other options. See also :ref:`attachments`.
.. qpdf:option:: --show-attachment=key
.. help: export an embedded file
Write the contents of the specified attachment to standard
output as binary data. Get the key with --list-attachments.
Write the contents of the specified attachment to standard output
as binary data. The key should match one of the keys shown by
:qpdf:ref:`--list-attachments`. If this option is given more than
once, only the last attachment will be shown. See also
:ref:`attachments`.
.. _json-options:
JSON Options
------------
.. help-topic json: JSON output for PDF information
Show information about the PDF file in JSON format. Please see the
JSON chapter in the qpdf manual for details.
It is possible to view information about PDF files in a JSON format.
See :ref:`json` for details about the qpdf JSON format.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --json[=version]
.. help: show file in JSON format
Generate a JSON representation of the file. This is described in
depth in the JSON section of the manual. "version" may be a
specific version or "latest". Run qpdf --json-help for a
description of the generated JSON object.
Generate a JSON representation of the file. This is described in
depth in :ref:`json`. The version parameter can be used to specify
which version of the qpdf JSON format should be output. The only
supported value is ``1``, but it's possible that a new JSON output
version will be added in a future version. You can also specify
``latest`` to use the latest JSON version. For backward
compatibility, the default value is ``1``. Use the
:qpdf:ref:`--json-help` option to get a description of the JSON
object.
.. qpdf:option:: --json-help
.. help: show format of JSON output
Describe the format of the JSON output by writing to standard
output a JSON object with the same keys and with values
containing descriptive text.
Describe the format of the JSON output by writing to standard
output a JSON object with the same structure with the same keys as
the JSON generated by qpdf. In the output written by
``--json-help``, each key's value is a description of the key. The
specific contract guaranteed by qpdf in its JSON representation is
explained in more detail in the :ref:`json`.
.. qpdf:option:: --json-key=key
.. help: limit which keys are in JSON output
This option is repeatable. If given, only the specified
top-level keys will be included in the JSON output. Otherwise,
all keys will be included.
This option is repeatable. If given, only the specified top-level
keys will be included in the JSON output. Otherwise, all keys will
be included. ``version`` and ``parameters`` will always appear in
the output.
.. qpdf:option:: --json-object={trailer|obj[,gen]}
.. help: limit which objects are in JSON
This option is repeatable. If given, only specified objects will
be shown in the "objects" key of the JSON output. Otherwise, all
objects will be shown.
This option is repeatable. If given, only specified objects will
be shown in the "``objects``" key of the JSON output. Otherwise, all
objects will be shown.
.. qpdf:option:: --job-json-help
.. help: show format of job JSON
Describe the format of the QPDFJob JSON input.
Describe the format of the QPDFJob JSON input. QXXXQ doc ref.
.. _test-options:
Options for Testing or Debugging
--------------------------------
.. help-topic testing: options for testing or debugging
The options below are useful when writing automated test code that
includes files created by qpdf or when testing qpdf itself.
The options below are useful when writing automated test code that
includes files created by qpdf or when testing qpdf itself. When
changes are made to qpdf, care is taken to avoid gratuitously changing
the output of PDF files. This is to make it easier to do direct
comparisons in test suites with files created by qpdf. However, there
are no guarantees that the PDF output won't change such as in the
event of a bug fix or feature enhancement to some aspect of the output
that qpdf creates.
.. _idempotency:
Idempotency
~~~~~~~~~~~
Note about idempotency of byte-for-byte content: there is no
expectation that qpdf is idempotent in the general case. In other
words, there is no expectation that, when qpdf is run on its own
output, it will create *byte-for-byte* identical output, even though
it will create semantically identical files. There are a variety of
reasons for this including document ID generation, which includes a
random element, as well as the interaction of stream length encoding
with dictionary key sorting.
It is possible to get idempotent behavior by using the
:qpdf:ref:`--static-id` or :qpdf:ref:`--deterministic-id` option with
qpdf and running it *three* times so that you are processing the
output of qpdf on its own previous output. For example, in this
sequence of commands:
::
qpdf any-file.pdf 1.pdf
qpdf --static-id 1.pdf 2.pdf
qpdf --static-id 2.pdf 3.pdf
the files :file:`2.pdf` and :file:`3.pdf` should be *byte-for-byte*
identical. The qpdf test suite relies on this behavior. See also
:qpdf:ref:`--static-aes-iv`.
Related Options
~~~~~~~~~~~~~~~
.. qpdf:option:: --static-id
.. help: use a fixed document ID
Use a fixed value for the document ID. This is intended for
testing only. Never use it for production files. See also
qpdf --help=--deterministic-id.
Use a fixed value for the document ID (``/ID`` in the trailer).
**This is intended for testing only. Never use it for production
files.** If you are trying to get the same ID each time for a given
file and you are not generating encrypted files, consider using the
:qpdf:ref:`--deterministic-id` option.
.. qpdf:option:: --static-aes-iv
.. help: use a fixed AES vector
Use a static initialization vector for AES-CBC. This is intended
for testing only so that output files can be reproducible. Never
use it for production files. This option is not secure since it
significantly weakens the encryption.
Use a static initialization vector for AES-CBC. This is intended
for testing only so that output files can be reproducible. Never
use it for production files. **This option in particular is not
secure since it significantly weakens the encryption.** When
combined with :qpdf:ref:`--static-id` and using the three-step
process described in :ref:`idempotency`, it is possible to create
byte-for-byte idempotent output with PDF files that use 256-bit
encryption to assist with creating reproducible test suites.
.. qpdf:option:: --linearize-pass1=file
.. help: save pass 1 of linearization
Write the first pass of linearization to the named file. The
resulting file is not a valid PDF file. This option is useful only
for debugging qpdf.
Write the first pass of linearization to the named file. *The
resulting file is not a valid PDF file.* This option is useful only
for debugging ``QPDFWriter``'s linearization code. When qpdf
linearizes files, it writes the file in two passes, using the first
pass to calculate sizes and offsets that are required for hint
tables and the linearization dictionary. Ordinarily, the first pass
is discarded. This option enables it to be captured, allowing
inspection of the file before values calculated in pass 1 are
inserted into the file for pass 2.
.. _unicode-passwords:
Unicode Passwords
-----------------
At the library API level, all methods that perform encryption and
decryption interpret passwords as strings of bytes. It is up to the
caller to ensure that they are appropriately encoded. Starting with qpdf
version 8.4.0, qpdf will attempt to make this easier for you when
interacting with qpdf via its command line interface. The PDF specification
requires passwords used to encrypt files with 40-bit or 128-bit
encryption to be encoded with PDF Doc encoding. This encoding is a
single-byte encoding that supports ISO-Latin-1 and a handful of other
commonly used characters. It has a large overlap with Windows ANSI but
is not exactly the same. There is generally no way to provide PDF Doc
encoded strings on the command line. As such, qpdf versions prior to
8.4.0 would often create PDF files that couldn't be opened with other
software when given a password with non-ASCII characters to encrypt a
file with 40-bit or 128-bit encryption. Starting with qpdf 8.4.0, qpdf
recognizes the encoding of the parameter and transcodes it as needed.
The rest of this section provides the details about exactly how qpdf
behaves. Most users will not need to know this information, but it might
be useful if you have been working around qpdf's old behavior or if you
are using qpdf to generate encrypted files for testing other PDF
software.
A note about Windows: when qpdf builds, it attempts to determine what it
has to do to use ``wmain`` instead of ``main`` on Windows. The ``wmain``
function is an alternative entry point that receives all arguments as
UTF-16-encoded strings. When qpdf starts up this way, it converts all
the strings to UTF-8 encoding and then invokes the regular main. This
means that, as far as qpdf is concerned, it receives its command-line
arguments with UTF-8 encoding, just as it would in any modern Linux or
UNIX environment.
If a file is being encrypted with 40-bit or 128-bit encryption and the
supplied password is not a valid UTF-8 string, qpdf will fall back to
the behavior of interpreting the password as a string of bytes. If you
have old scripts that encrypt files by passing the output of
:command:`iconv` to qpdf, you no longer need to do that,
but if you do, qpdf should still work. The only exception would be for
the extremely unlikely case of a password that is encoded with a
single-byte encoding but also happens to be valid UTF-8. Such a password
would contain strings of even numbers of characters that alternate
between accented letters and symbols. In the extremely unlikely event
that you are intentionally using such passwords and qpdf is thwarting
you by interpreting them as UTF-8, you can use
:samp:`--password-mode=bytes` to suppress qpdf's
automatic behavior.
The :qpdf:ref:`--password-mode` option, as described earlier
in this chapter, can be used to change qpdf's interpretation of supplied
passwords. There are very few reasons to use this option. One would be
the unlikely case described in the previous paragraph in which the
supplied password happens to be valid UTF-8 but isn't supposed to be
UTF-8. Your best bet would be just to provide the password as a valid
UTF-8 string, but you could also use
:samp:`--password-mode=bytes`. Another reason to use
:samp:`--password-mode=bytes` would be to intentionally
generate PDF files encrypted with passwords that are not properly
encoded. The qpdf test suite does this to generate invalid files for the
purpose of testing its password recovery capability. If you were trying
to create intentionally incorrect files for a similar purposes, the
:samp:`bytes` password mode can enable you to do this.
When qpdf attempts to decrypt a file with a password that contains
non-ASCII characters, it will generate a list of alternative passwords
by attempting to interpret the password as each of a handful of
different coding systems and then transcode them to the required format.
This helps to compensate for the supplied password being given in the
wrong coding system, such as would happen if you used the
:command:`iconv` workaround that was previously needed.
It also generates passwords by doing the reverse operation: translating
from correct in incorrect encoding of the password. This would enable
qpdf to decrypt files using passwords that were improperly encoded by
whatever software encrypted the files, including older versions of qpdf
invoked without properly encoded passwords. The combination of these two
recovery methods should make qpdf transparently open most encrypted
files with the password supplied correctly but in the wrong coding
system. There are no real downsides to this behavior, but if you don't
want qpdf to do this, you can use the
:qpdf:ref:`--suppress-password-recovery` option. One reason
to do that is to ensure that you know the exact password that was used
to encrypt the file.
With these changes, qpdf now generates compliant passwords in most
cases. There are still some exceptions. In particular, the PDF
specification directs compliant writers to normalize Unicode passwords
and to perform certain transformations on passwords with bidirectional
text. Implementing this functionality requires using a real Unicode
library like ICU. If a client application that uses qpdf wants to do
this, the qpdf library will accept the resulting passwords, but qpdf
will not perform these transformations itself. It is possible that this
will be addressed in a future version of qpdf. The ``QPDFWriter``
methods that enable encryption on the output file accept passwords as
strings of bytes.
Please note that the :qpdf:ref:`--password-is-hex-key` option is
unrelated to all this. That flag bypasses the normal process of going
from password to encryption key entirely, allowing the raw
encryption key to be specified directly. That behavior is useful for
forensic purposes or for brute-force recovery of files with unknown
passwords and has nothing to do with the document's actual passwords.
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