diff --git a/Makefile b/Makefile
index e1e09738..6a6412dc 100644
--- a/Makefile
+++ b/Makefile
@@ -100,7 +100,7 @@ $(foreach B,$(BUILD_ITEMS),$(eval \
 DISTFILES = doc/qpdf-manual.html doc/qpdf-manual.pdf
 distfiles.zip: $(DISTFILES)
 	$(RM) distfiles.zip
-	zip distfiles.zip $(DISTFILES)
+	zip -r distfiles.zip $(DISTFILES) doc/_static
 
 distclean: clean
 	$(RM) -r autoconf.mk autom4te.cache config.log config.status libtool
diff --git a/TODO b/TODO
index 5b30f9f0..b29a5a5b 100644
--- a/TODO
+++ b/TODO
@@ -42,20 +42,6 @@ Correct placement of comment: <!-- This section is referenced in QPDFObjectHandl
 <firstterm> -> just use literal
 <replaceable> -> Make sure in :file: or :samp:, then use {}
 
-Build:
-
-apt install python3-pip texlive-latex-extra latexmk
-pip install sphinx
-
-sphinx-build -M help . .
-sphinx-build -M latexpdf source build
-sphinx-build -M html source build
-sphinx-build -M singlehtml source build
-
-autoconf should detect sphinx and its dependencies, not fop, etc.
-Remove VALIDATE_DOC
-Fix installation of documentation in doc
-
 Additional cleanup:
 
 * Indices and tables section
diff --git a/aclocal.m4 b/aclocal.m4
index e8d099d4..3fbe0b65 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1,6 +1,6 @@
-# generated automatically by aclocal 1.16.1 -*- Autoconf -*-
+# generated automatically by aclocal 1.16.4 -*- Autoconf -*-
 
-# Copyright (C) 1996-2018 Free Software Foundation, Inc.
+# Copyright (C) 1996-2021 Free Software Foundation, Inc.
 
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
diff --git a/appimage/Dockerfile b/appimage/Dockerfile
index c607ca21..51221908 100644
--- a/appimage/Dockerfile
+++ b/appimage/Dockerfile
@@ -1,11 +1,13 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
+ENV DEBIAN_FRONTEND=noninteractive
 RUN apt-get update && \
     apt-get -y install screen autoconf git sudo \
        build-essential zlib1g-dev libjpeg-dev libgnutls28-dev \
-       docbook-xsl fop xsltproc \
+       python3-pip texlive-latex-extra latexmk \
        inkscape imagemagick busybox-static wget fuse && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
+RUN pip3 install sphinx
 COPY entrypoint /entrypoint
 RUN chmod +x /entrypoint
 ENTRYPOINT [ "/entrypoint" ]
diff --git a/appimage/build-appimage b/appimage/build-appimage
index 03039ed1..04fa805b 100755
--- a/appimage/build-appimage
+++ b/appimage/build-appimage
@@ -43,24 +43,25 @@ if [ "x$1" == "x--sign" ]; then
 fi
 
 
-# Check if we are on Ubuntu Trusty
+# Check Ubuntu Distribution
 _osversion=$(cat /etc/os-release | grep PRETTY_NAME | awk -F'=' '{print $2}' | sed 's#"##g')
 
 # Warn users building the AppImage locally:
-if [[ ! $_osversion =~ Ubuntu\ 16.04.*\ LTS ]]; then
+if [[ ! $_osversion =~ Ubuntu\ 18.04.*\ LTS ]]; then
 set +x
     echo ""
     #    0         1         2         3         4         5         6         7
     #    01234567890123456789012345678901234567890123456789012345678901234567890123456789
     echo "+===========================================================================+"
     echo "|| WARNING: You are about to build a QPDF AppImage on a system which is    ||"
-    echo "|| NOT Ubuntu 16.04 LTS ('Xenial').                                        ||"
+    echo "|| NOT Ubuntu 18.04 LTS.                                                   ||"
     echo "||                                                                         ||"
     echo "||    It is recommended that you use a distribution that is at least a     ||"
     echo "||    few years old to maximize the number of Linux distributions the      ||"
     echo "||    resulting AppImage will work on. AppImages often don't work on       ||"
     echo "||    distributions older than the one they were built on because of       ||"
-    echo "||    standard library differences.                                        ||"
+    echo "||    standard library differences. The oldest supported Ubuntu LTS is     ||"
+    echo "||    a good option.                                                       ||"
     echo "+===========================================================================+"
     echo ""
 set -x
diff --git a/autoconf.mk.in b/autoconf.mk.in
index 2836b4f1..34a19801 100644
--- a/autoconf.mk.in
+++ b/autoconf.mk.in
@@ -34,13 +34,9 @@ LIBTOOL=@LIBTOOL@
 USE_CRYPTO_NATIVE=@USE_CRYPTO_NATIVE@
 USE_CRYPTO_OPENSSL=@USE_CRYPTO_OPENSSL@
 USE_CRYPTO_GNUTLS=@USE_CRYPTO_GNUTLS@
-DOCBOOKX_DTD=@DOCBOOKX_DTD@
-FOP=@FOP@
-XSLTPROC=@XSLTPROC@
-XMLLINT=@XMLLINT@
+SPHINX=@SPHINX@
 BUILD_HTML=@BUILD_HTML@
 BUILD_PDF=@BUILD_PDF@
-VALIDATE_DOC=@VALIDATE_DOC@
 OSS_FUZZ=@OSS_FUZZ@
 QPDF_SKIP_TEST_COMPARE_IMAGES=@QPDF_SKIP_TEST_COMPARE_IMAGES@
 BUILDRULES=@BUILDRULES@
diff --git a/autofiles.sums b/autofiles.sums
index 6d0367a3..a0476d70 100644
--- a/autofiles.sums
+++ b/autofiles.sums
@@ -1,5 +1,5 @@
-e8f33e2b17d8c04fc1c160e9a92e7f1e48e433467f734629cdbb873f2d6fa676  configure.ac
-d3f9ee6f6f0846888d9a10fd3dad2e4b1258be84205426cf04d7cef02d61dad7  aclocal.m4
+44c66263db20dec40cefe94df4f9f9effe7410f20865cd53cf89268f6a98010f  configure.ac
+a45b129101efb46d7ac59ca2cf12d137a5742c2593ea11ebb32401aefd915b96  aclocal.m4
 c12d837479fa9a3fa4c278b6dc7d6b449503d663e0f0d294305595a51ff43f70  libqpdf/qpdf/qpdf-config.h.in
 5297971a0ef90bcd5563eb3f7127a032bb76d3ae2af7258bf13479caf8983a60  m4/ax_cxx_compile_stdcxx.m4
 35bc5c645dc42d47f2daeea06f8f3e767c8a1aee6a35eb2b4854fd2ce66c3413  m4/ax_random_device.m4
diff --git a/build-scripts/build-linux b/build-scripts/build-linux
index 98d001a0..448c5871 100755
--- a/build-scripts/build-linux
+++ b/build-scripts/build-linux
@@ -3,8 +3,9 @@ set -ex
 sudo apt-get update
 sudo apt-get -y install \
    autoconf build-essential zlib1g-dev libjpeg-dev libgnutls28-dev \
-   libssl-dev docbook-xsl fop xsltproc libxml2-utils inkscape imagemagick \
-   libtiff-tools ghostscript
+   libssl-dev python3-pip texlive-latex-extra latexmk \
+   inkscape imagemagick libtiff-tools ghostscript
+pip3 install sphinx
 ./configure --enable-werror --enable-doc-maintenance \
     --enable-crypto-native --enable-crypto-openssl --enable-crypto-gnutls \
     --enable-show-failed-test-output --enable-test-compare-images
diff --git a/build-scripts/make-distfiles b/build-scripts/make-distfiles
index 26ef161d..f30f4595 100755
--- a/build-scripts/make-distfiles
+++ b/build-scripts/make-distfiles
@@ -4,7 +4,8 @@ set -ex
 sudo apt-get update
 sudo apt-get -y install \
    autoconf build-essential zlib1g-dev libjpeg-dev \
-   docbook-xsl fop xsltproc libxml2-utils inkscape imagemagick
+   python3-pip texlive-latex-extra latexmk inkscape imagemagick
+pip3 install sphinx
 ./configure --enable-doc-maintenance
 make -j$(nproc) distfiles.zip
 build-scripts/download-external-libs
diff --git a/configure b/configure
index ce153db2..eaf6a7f5 100755
--- a/configure
+++ b/configure
@@ -631,15 +631,12 @@ ac_includes_default="\
 ac_subst_vars='LTLIBOBJS
 LIBOBJS
 OSS_FUZZ
-VALIDATE_DOC
 BUILD_PDF
 BUILD_HTML
-XMLLINT
-XSLTPROC
-FOP
-DOCBOOKX_DTD
-DOCBOOK_FO
-DOCBOOK_XHTML
+SPHINX
+LATEXMK
+PDFLATEX
+LATEX
 SHOW_FAILED_TEST_OUTPUT
 QPDF_SKIP_TEST_COMPARE_IMAGES
 DEFAULT_CRYPTO
@@ -794,12 +791,9 @@ enable_crypto_gnutls
 with_default_crypto
 enable_test_compare_images
 enable_show_failed_test_output
-with_docbook_xsl
-with_docbookx_dtd
 enable_doc_maintenance
 enable_html_doc
 enable_pdf_doc
-enable_validate_doc
 enable_oss_fuzz
 '
       ac_precious_vars='build_alias
@@ -1497,7 +1491,6 @@ Optional Features:
                           if set, enables all documentation options
   --enable-html-doc       whether to build HTML documents
   --enable-pdf-doc        whether to build PDF documents
-  --enable-validate-doc   whether to validate xml document source
   --enable-oss-fuzz       if set, build static fuzzers for oss-fuzz
 
 Optional Packages:
@@ -1523,9 +1516,6 @@ Optional Packages:
   --with-default-crypto=provider
                           which crypto provider to use by default; see
                           README.md
-  --with-docbook-xsl=DIR  location of docbook 4.x xml stylesheets
-  --with-docbookx-dtd=FILE
-                          location of docbook 4.x xml DTD
 
 Some influential environment variables:
   CC          C compiler command
@@ -2650,8 +2640,6 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 ac_config_files="$ac_config_files autoconf.mk"
 
-ac_config_files="$ac_config_files manual/html.xsl manual/print.xsl"
-
 ac_config_files="$ac_config_files libqpdf.pc"
 
 ac_config_files="$ac_config_files libqpdf.map"
@@ -18449,69 +18437,15 @@ else
 fi
 
 
-
-# Check whether --with-docbook-xsl was given.
-if test "${with_docbook_xsl+set}" = set; then :
-  withval=$with_docbook_xsl; DOCBOOK_XSL=$withval
-else
-  DOCBOOK_XSL=/usr/share/xml/docbook/stylesheet/nwalsh
-fi
-
-
-DOCBOOK_XHTML=
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for xml to xhtml docbook stylesheets" >&5
-$as_echo_n "checking for xml to xhtml docbook stylesheets... " >&6; }
-if test -f "$DOCBOOK_XSL/xhtml/docbook.xsl"; then
-   DOCBOOK_XHTML="$DOCBOOK_XSL/xhtml/docbook.xsl"
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $DOCBOOK_XHTML" >&5
-$as_echo "$DOCBOOK_XHTML" >&6; }
-else
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-DOCBOOK_FO=
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for xml to fo docbook stylesheets" >&5
-$as_echo_n "checking for xml to fo docbook stylesheets... " >&6; }
-if test -f "$DOCBOOK_XSL/fo/docbook.xsl"; then
-   DOCBOOK_FO="$DOCBOOK_XSL/fo/docbook.xsl"
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $DOCBOOK_FO" >&5
-$as_echo "$DOCBOOK_FO" >&6; }
-else
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-DOCBOOKX_DTD=
-
-
-# Check whether --with-docbookx-dtd was given.
-if test "${with_docbookx_dtd+set}" = set; then :
-  withval=$with_docbookx_dtd; DOCBOOKX_DTD=$withval
-else
-  DOCBOOKX_DTD=/usr/share/xml/docbook/schema/dtd/4/docbookx.dtd
-fi
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for docbook 4.x xml DTD" >&5
-$as_echo_n "checking for docbook 4.x xml DTD... " >&6; }
-if test -f "$DOCBOOKX_DTD"; then
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $DOCBOOKX_DTD" >&5
-$as_echo "$DOCBOOKX_DTD" >&6; }
-else
-   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-# Extract the first word of "fop", so it can be a program name with args.
-set dummy fop; ac_word=$2
+# Extract the first word of "latex", so it can be a program name with args.
+set dummy latex; ac_word=$2
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 $as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_FOP+:} false; then :
+if ${ac_cv_prog_LATEX+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  if test -n "$FOP"; then
-  ac_cv_prog_FOP="$FOP" # Let the user override the test.
+  if test -n "$LATEX"; then
+  ac_cv_prog_LATEX="$LATEX" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
@@ -18520,7 +18454,7 @@ do
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_FOP="fop"
+    ac_cv_prog_LATEX="latex"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -18530,25 +18464,25 @@ IFS=$as_save_IFS
 
 fi
 fi
-FOP=$ac_cv_prog_FOP
-if test -n "$FOP"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $FOP" >&5
-$as_echo "$FOP" >&6; }
+LATEX=$ac_cv_prog_LATEX
+if test -n "$LATEX"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $LATEX" >&5
+$as_echo "$LATEX" >&6; }
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 fi
 
 
-# Extract the first word of "xsltproc", so it can be a program name with args.
-set dummy xsltproc; ac_word=$2
+# Extract the first word of "pdflatex", so it can be a program name with args.
+set dummy pdflatex; ac_word=$2
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 $as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_XSLTPROC+:} false; then :
+if ${ac_cv_prog_PDFLATEX+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  if test -n "$XSLTPROC"; then
-  ac_cv_prog_XSLTPROC="$XSLTPROC" # Let the user override the test.
+  if test -n "$PDFLATEX"; then
+  ac_cv_prog_PDFLATEX="$PDFLATEX" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
@@ -18557,7 +18491,7 @@ do
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_XSLTPROC="xsltproc"
+    ac_cv_prog_PDFLATEX="pdflatex"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -18567,25 +18501,25 @@ IFS=$as_save_IFS
 
 fi
 fi
-XSLTPROC=$ac_cv_prog_XSLTPROC
-if test -n "$XSLTPROC"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $XSLTPROC" >&5
-$as_echo "$XSLTPROC" >&6; }
+PDFLATEX=$ac_cv_prog_PDFLATEX
+if test -n "$PDFLATEX"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PDFLATEX" >&5
+$as_echo "$PDFLATEX" >&6; }
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 fi
 
 
-# Extract the first word of "xmllint", so it can be a program name with args.
-set dummy xmllint; ac_word=$2
+# Extract the first word of "latexmk", so it can be a program name with args.
+set dummy latexmk; ac_word=$2
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 $as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_XMLLINT+:} false; then :
+if ${ac_cv_prog_LATEXMK+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  if test -n "$XMLLINT"; then
-  ac_cv_prog_XMLLINT="$XMLLINT" # Let the user override the test.
+  if test -n "$LATEXMK"; then
+  ac_cv_prog_LATEXMK="$LATEXMK" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
@@ -18594,7 +18528,7 @@ do
   test -z "$as_dir" && as_dir=.
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_XMLLINT="xmllint"
+    ac_cv_prog_LATEXMK="latexmk"
     $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -18604,10 +18538,47 @@ IFS=$as_save_IFS
 
 fi
 fi
-XMLLINT=$ac_cv_prog_XMLLINT
-if test -n "$XMLLINT"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $XMLLINT" >&5
-$as_echo "$XMLLINT" >&6; }
+LATEXMK=$ac_cv_prog_LATEXMK
+if test -n "$LATEXMK"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $LATEXMK" >&5
+$as_echo "$LATEXMK" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+# Extract the first word of "sphinx-build", so it can be a program name with args.
+set dummy sphinx-build; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_SPHINX+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$SPHINX"; then
+  ac_cv_prog_SPHINX="$SPHINX" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_SPHINX="sphinx-build"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+SPHINX=$ac_cv_prog_SPHINX
+if test -n "$SPHINX"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $SPHINX" >&5
+$as_echo "$SPHINX" >&6; }
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
@@ -18653,19 +18624,6 @@ else
   BUILD_PDF=$doc_default
 fi
 
-VALIDATE_DOC=0
-
-# Check whether --enable-validate-doc was given.
-if test "${enable_validate_doc+set}" = set; then :
-  enableval=$enable_validate_doc; if test "$enableval" = "yes"; then
-      VALIDATE_DOC=1;
-    else
-      VALIDATE_DOC=0;
-    fi
-else
-  VALIDATE_DOC=$doc_default
-fi
-
 
 
 # Check whether --enable-oss-fuzz was given.
@@ -18680,38 +18638,31 @@ else
 fi
 
 
-if test "$VALIDATE_DOC" = "1"; then
-   if test "$XMLLINT" = ""; then
-      MISSING_XMLLINT=1
-      MISSING_ANY=1
-   fi
-fi
 if test "$BUILD_HTML" = "1"; then
-   if test "$XSLTPROC" = ""; then
-      MISSING_XSLTPROC=1
-      MISSING_ANY=1
-   fi
-   if test "$DOCBOOK_XHTML" = ""; then
-      MISSING_DOCBOOK_XHTML=1
+   if test "$SPHINX" = ""; then
+      MISSING_SPHINX=1
       MISSING_ANY=1
    fi
 fi
 if test "$BUILD_PDF" = "1"; then
-   if test "$XSLTPROC" = ""; then
-      MISSING_XSLTPROC=1
+   if test "$SPHINX" = ""; then
+      MISSING_SPHINX=1
       MISSING_ANY=1
    fi
-   if test "$DOCBOOK_FO" = ""; then
-      MISSING_DOCBOOK_FO=1
+   if test "$LATEX" = ""; then
+      MISSING_LATEX=1
       MISSING_ANY=1
    fi
-   if test "$FOP" = ""; then
-      MISSING_FOP=1
+   if test "$LATEXMK" = ""; then
+      MISSING_LATEXMK=1
+      MISSING_ANY=1
+   fi
+   if test "$PDFLATEX" = ""; then
+      MISSING_PDFLATEX=1
       MISSING_ANY=1
    fi
 fi
 
-
 if test "$MISSING_ANY" = "1"; then
   ISSUE_WARNINGS=1
 fi
@@ -18745,29 +18696,24 @@ if test "$MISSING_JPEG" = "1"; then
 $as_echo "$as_me: WARNING: unable to find required library jpeg" >&2;}
 fi
 
-if test "$MISSING_DOCBOOK_FO" = "1"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: docbook fo stylesheets are required to build PDF documentation" >&5
-$as_echo "$as_me: WARNING: docbook fo stylesheets are required to build PDF documentation" >&2;}
+if test "$MISSING_LATEX" = "1"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: latex is required to build PDF documentation" >&5
+$as_echo "$as_me: WARNING: latex is required to build PDF documentation" >&2;}
 fi
 
-if test "$MISSING_DOCBOOK_XHTML" = "1"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: docbook xhmtl stylesheets are required to build HTML documentation" >&5
-$as_echo "$as_me: WARNING: docbook xhmtl stylesheets are required to build HTML documentation" >&2;}
+if test "$MISSING_LATEXMK" = "1"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: latexmk is required to build PDF documentation" >&5
+$as_echo "$as_me: WARNING: latexmk is required to build PDF documentation" >&2;}
 fi
 
-if test "$MISSING_FOP" = "1"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: apache fop is required to build PDF documentation" >&5
-$as_echo "$as_me: WARNING: apache fop is required to build PDF documentation" >&2;}
+if test "$MISSING_PDFLATEX" = "1"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: pdflatex is required to build PDF documentation" >&5
+$as_echo "$as_me: WARNING: pdflatex is required to build PDF documentation" >&2;}
 fi
 
-if test "$MISSING_XMLLINT" = "1"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: xmllint is required to validate documentation" >&5
-$as_echo "$as_me: WARNING: xmllint is required to validate documentation" >&2;}
-fi
-
-if test "$MISSING_XSLTPROC" = "1"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: xsltproc is required to build documentation" >&5
-$as_echo "$as_me: WARNING: xsltproc is required to build documentation" >&2;}
+if test "$MISSING_SPHINX" = "1"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: sphinx-build is required to build documentation" >&5
+$as_echo "$as_me: WARNING: sphinx-build is required to build documentation" >&2;}
 fi
 
 if test "$ISSUE_WARNINGS" = "1"; then
@@ -19871,8 +19817,6 @@ for ac_config_target in $ac_config_targets
 do
   case $ac_config_target in
     "autoconf.mk") CONFIG_FILES="$CONFIG_FILES autoconf.mk" ;;
-    "manual/html.xsl") CONFIG_FILES="$CONFIG_FILES manual/html.xsl" ;;
-    "manual/print.xsl") CONFIG_FILES="$CONFIG_FILES manual/print.xsl" ;;
     "libqpdf.pc") CONFIG_FILES="$CONFIG_FILES libqpdf.pc" ;;
     "libqpdf.map") CONFIG_FILES="$CONFIG_FILES libqpdf.map" ;;
     "libqpdf/qpdf/qpdf-config.h") CONFIG_HEADERS="$CONFIG_HEADERS libqpdf/qpdf/qpdf-config.h" ;;
diff --git a/configure.ac b/configure.ac
index 8d81ac3a..5e868dce 100644
--- a/configure.ac
+++ b/configure.ac
@@ -6,7 +6,6 @@ AC_INIT([qpdf],[10.4.0])
 
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_FILES([autoconf.mk])
-AC_CONFIG_FILES([manual/html.xsl manual/print.xsl])
 AC_CONFIG_FILES([libqpdf.pc])
 AC_CONFIG_FILES([libqpdf.map])
 AC_CONFIG_HEADERS([libqpdf/qpdf/qpdf-config.h])
@@ -795,48 +794,10 @@ AC_ARG_ENABLE(show-failed-test-output,
     fi],
    [SHOW_FAILED_TEST_OUTPUT=0])
 
-AC_ARG_WITH(docbook-xsl,
-   AS_HELP_STRING([--with-docbook-xsl=DIR],
-		  [location of docbook 4.x xml stylesheets]),
-   [DOCBOOK_XSL=$withval],
-   [DOCBOOK_XSL=/usr/share/xml/docbook/stylesheet/nwalsh])
-
-DOCBOOK_XHTML=
-AC_SUBST(DOCBOOK_XHTML)
-AC_MSG_CHECKING(for xml to xhtml docbook stylesheets)
-if test -f "$DOCBOOK_XSL/xhtml/docbook.xsl"; then
-   DOCBOOK_XHTML="$DOCBOOK_XSL/xhtml/docbook.xsl"
-   AC_MSG_RESULT($DOCBOOK_XHTML)
-else
-   AC_MSG_RESULT(no)
-fi
-DOCBOOK_FO=
-AC_SUBST(DOCBOOK_FO)
-AC_MSG_CHECKING(for xml to fo docbook stylesheets)
-if test -f "$DOCBOOK_XSL/fo/docbook.xsl"; then
-   DOCBOOK_FO="$DOCBOOK_XSL/fo/docbook.xsl"
-   AC_MSG_RESULT($DOCBOOK_FO)
-else
-   AC_MSG_RESULT(no)
-fi
-
-DOCBOOKX_DTD=
-AC_SUBST(DOCBOOKX_DTD)
-AC_ARG_WITH(docbookx-dtd,
-   AS_HELP_STRING([--with-docbookx-dtd=FILE],
-		  [location of docbook 4.x xml DTD]),
-   [DOCBOOKX_DTD=$withval],
-   [DOCBOOKX_DTD=/usr/share/xml/docbook/schema/dtd/4/docbookx.dtd])
-AC_MSG_CHECKING(for docbook 4.x xml DTD)
-if test -f "$DOCBOOKX_DTD"; then
-   AC_MSG_RESULT($DOCBOOKX_DTD)
-else
-   AC_MSG_RESULT(no)
-fi
-
-AC_CHECK_PROG(FOP,fop,fop,[])
-AC_CHECK_PROG(XSLTPROC,xsltproc,xsltproc,[])
-AC_CHECK_PROG(XMLLINT,xmllint,xmllint,[])
+AC_CHECK_PROG(LATEX,latex,latex,[])
+AC_CHECK_PROG(PDFLATEX,pdflatex,pdflatex,[])
+AC_CHECK_PROG(LATEXMK,latexmk,latexmk,[])
+AC_CHECK_PROG(SPHINX,sphinx-build,sphinx-build,[])
 
 AC_ARG_ENABLE(doc-maintenance,
    AS_HELP_STRING([--enable-doc-maintenance],
@@ -870,17 +831,6 @@ AC_ARG_ENABLE(pdf-doc,
       BUILD_PDF=0;
     fi],
    [BUILD_PDF=$doc_default])
-VALIDATE_DOC=0
-AC_SUBST(VALIDATE_DOC)
-AC_ARG_ENABLE(validate-doc,
-   AS_HELP_STRING([--enable-validate-doc],
-		  [whether to validate xml document source]),
-   [if test "$enableval" = "yes"; then
-      VALIDATE_DOC=1;
-    else
-      VALIDATE_DOC=0;
-    fi],
-   [VALIDATE_DOC=$doc_default])
 
 AC_SUBST(OSS_FUZZ)
 AC_ARG_ENABLE(oss-fuzz,
@@ -893,38 +843,31 @@ AC_ARG_ENABLE(oss-fuzz,
     fi],
    [OSS_FUZZ=0])
 
-if test "$VALIDATE_DOC" = "1"; then
-   if test "$XMLLINT" = ""; then
-      MISSING_XMLLINT=1
-      MISSING_ANY=1
-   fi
-fi
 if test "$BUILD_HTML" = "1"; then
-   if test "$XSLTPROC" = ""; then
-      MISSING_XSLTPROC=1
-      MISSING_ANY=1
-   fi
-   if test "$DOCBOOK_XHTML" = ""; then
-      MISSING_DOCBOOK_XHTML=1
+   if test "$SPHINX" = ""; then
+      MISSING_SPHINX=1
       MISSING_ANY=1
    fi
 fi
 if test "$BUILD_PDF" = "1"; then
-   if test "$XSLTPROC" = ""; then
-      MISSING_XSLTPROC=1
+   if test "$SPHINX" = ""; then
+      MISSING_SPHINX=1
       MISSING_ANY=1
    fi
-   if test "$DOCBOOK_FO" = ""; then
-      MISSING_DOCBOOK_FO=1
+   if test "$LATEX" = ""; then
+      MISSING_LATEX=1
       MISSING_ANY=1
    fi
-   if test "$FOP" = ""; then
-      MISSING_FOP=1
+   if test "$LATEXMK" = ""; then
+      MISSING_LATEXMK=1
+      MISSING_ANY=1
+   fi
+   if test "$PDFLATEX" = ""; then
+      MISSING_PDFLATEX=1
       MISSING_ANY=1
    fi
 fi
 
-
 if test "$MISSING_ANY" = "1"; then
   ISSUE_WARNINGS=1
 fi
@@ -953,24 +896,20 @@ if test "$MISSING_JPEG" = "1"; then
   AC_MSG_WARN(unable to find required library jpeg)
 fi
 
-if test "$MISSING_DOCBOOK_FO" = "1"; then
-  AC_MSG_WARN(docbook fo stylesheets are required to build PDF documentation)
+if test "$MISSING_LATEX" = "1"; then
+  AC_MSG_WARN(latex is required to build PDF documentation)
 fi
 
-if test "$MISSING_DOCBOOK_XHTML" = "1"; then
-  AC_MSG_WARN(docbook xhmtl stylesheets are required to build HTML documentation)
+if test "$MISSING_LATEXMK" = "1"; then
+  AC_MSG_WARN(latexmk is required to build PDF documentation)
 fi
 
-if test "$MISSING_FOP" = "1"; then
-  AC_MSG_WARN(apache fop is required to build PDF documentation)
+if test "$MISSING_PDFLATEX" = "1"; then
+  AC_MSG_WARN(pdflatex is required to build PDF documentation)
 fi
 
-if test "$MISSING_XMLLINT" = "1"; then
-  AC_MSG_WARN(xmllint is required to validate documentation)
-fi
-
-if test "$MISSING_XSLTPROC" = "1"; then
-  AC_MSG_WARN(xsltproc is required to build documentation)
+if test "$MISSING_SPHINX" = "1"; then
+  AC_MSG_WARN(sphinx-build is required to build documentation)
 fi
 
 if test "$ISSUE_WARNINGS" = "1"; then
diff --git a/make/installwin.mk b/make/installwin.mk
index 3ed541ae..4acf9e3f 100644
--- a/make/installwin.mk
+++ b/make/installwin.mk
@@ -17,9 +17,10 @@ installwin: all
 	cp qpdf/$(OUTPUT_DIR)/fix-qdf.exe $(DEST)/bin
 	cp include/qpdf/*.h $(DEST)/include/qpdf
 	cp include/qpdf/*.hh $(DEST)/include/qpdf
-	cp doc/stylesheet.css $(DEST)/doc
 	if [ -f doc/qpdf-manual.html ]; then \
+	    mkdir $(DEST)/doc/_static; \
 	    cp doc/qpdf-manual.html $(DEST)/doc; \
+	    cp doc/_static/* $(DEST)/doc/_static; \
 	fi
 	if [ -f doc/qpdf-manual.pdf ]; then \
 	    cp doc/qpdf-manual.pdf $(DEST)/doc; \
diff --git a/make/libtool.mk b/make/libtool.mk
index 2ff96f86..eda53732 100644
--- a/make/libtool.mk
+++ b/make/libtool.mk
@@ -120,6 +120,12 @@ install-libs: build_libqpdf
 
 # NOTE: If installing any new executables, remember to update the
 # lambda layer code in build-scripts/build-appimage.
+
+# NOTE: See comments in manual/build.mk about html documentation.
+
+# Ensure that installwin in make/installwin.mk is consistent with
+# this.
+
 install: all install-libs
 	./mkinstalldirs -m 0755 $(DESTDIR)$(bindir)
 	./mkinstalldirs -m 0755 $(DESTDIR)$(docdir)
@@ -133,9 +139,10 @@ install: all install-libs
 	$(LIBTOOL) --mode=install ./install-sh \
 		qpdf/$(OUTPUT_DIR)/fix-qdf \
 		$(DESTDIR)$(bindir)/fix-qdf
-	./install-sh -m 0644 doc/stylesheet.css $(DESTDIR)$(docdir)
 	if [ -f doc/qpdf-manual.html ]; then \
+		./mkinstalldirs -m 0755 $(DESTDIR)$(docdir)/_static; \
 		./install-sh -m 0644 doc/qpdf-manual.html $(DESTDIR)$(docdir); \
+		./install-sh -m 0644 doc/_static/* $(DESTDIR)$(docdir)/_static; \
 	fi
 	if [ -f doc/qpdf-manual.pdf ]; then \
 		./install-sh -m 0644 doc/qpdf-manual.pdf $(DESTDIR)$(docdir); \
diff --git a/make_dist b/make_dist
index d6e42332..60ce9842 100755
--- a/make_dist
+++ b/make_dist
@@ -78,7 +78,7 @@ if ($version ne $code_version)
 }
 if ($version ne $doc_version)
 {
-    print "$whoami: qpdf-manual.xml version = $doc_version\n";
+    print "$whoami: doc version = $doc_version\n";
     $version_error = 1;
 }
 if ($version ne $cli_version)
@@ -153,11 +153,11 @@ sub get_version_from_source
 
 sub get_version_from_manual
 {
-    my $fh = safe_open("manual/qpdf-manual.xml");
+    my $fh = safe_open("manual/conf.py");
     my $doc_version = 'unknown';
     while (<$fh>)
     {
-        if (m/swversion "([^\"]+)\"/)
+        if (m/release = '([^\']+)\'/)
         {
             $doc_version = $1;
             last;
diff --git a/manual/build.mk b/manual/build.mk
index 3911b8e2..89285b94 100644
--- a/manual/build.mk
+++ b/manual/build.mk
@@ -1,45 +1,55 @@
-INDOC = manual/qpdf-manual
-OUTDOC = manual/$(OUTPUT_DIR)/qpdf-manual
+DOC_OUT := manual/$(OUTPUT_DIR)
+S_HTML_OUT := $(DOC_OUT)/singlehtml
+S_HTML_TARGET := $(S_HTML_OUT)/index.html
+HTML_OUT := $(DOC_OUT)/html
+HTML_TARGET := $(HTML_OUT)/index.html
+PDF_OUT := $(DOC_OUT)/latex
+PDF_TARGET := $(PDF_OUT)/qpdf.pdf
 
 TARGETS_manual := doc/qpdf.1 doc/fix-qdf.1 doc/zlib-flate.1
 ifeq ($(BUILD_HTML),1)
-TARGETS_manual += doc/qpdf-manual.html
+TARGETS_manual += doc/qpdf-manual.html $(HTML_TARGET)
 endif
 ifeq ($(BUILD_PDF),1)
 TARGETS_manual += doc/qpdf-manual.pdf
 endif
 
-VALIDATE=manual/$(OUTPUT_DIR)/validate
+# Prevent targets that run $(SPHINX) from running in parallel by using
+# order-only dependencies (the dependencies listed after the |) to
+# avoid clashes in temporary files that cause the build to fail with
+# the error "_pickle.UnpicklingError: pickle data was truncated"
+$(HTML_TARGET): manual/index.rst
+	$(SPHINX) -M html manual $(DOC_OUT) -W
 
-ifeq ($(VALIDATE_DOC),1)
+$(S_HTML_TARGET): manual/index.rst | $(HTML_TARGET)
+	$(SPHINX) -M singlehtml manual $(DOC_OUT) -W
 
-$(VALIDATE): $(INDOC).xml
-	$(XMLLINT) --noout --dtdvalid $(DOCBOOKX_DTD) $<
-	touch $(VALIDATE)
+$(PDF_TARGET): manual/index.rst | $(S_HTML_TARGET) $(HTML_TARGET)
+	$(SPHINX) -M latexpdf manual $(DOC_OUT) -W
 
-else
+# This depends on sphinx-build's singlehtml target creating index.html
+# and a _static directory. If that changes, this code has to be
+# adjusted. It will also be necessary to adjust the install target in
+# make/libtool.mk.
+doc/qpdf-manual.html: $(S_HTML_TARGET)
+	mkdir -p doc
+	@if [ "$(shell find $(S_HTML_OUT)/ -mindepth 1 -type d -print)" != \
+             "$(S_HTML_OUT)/_static" ]; then \
+	    echo "***"; \
+	    echo Expected only directory in $(S_HTML_OUT) to be _static; \
+	    echo "***"; \
+	    false; \
+	fi
+	cp $< $@
+	mkdir -p doc/_static
+	cp -p $(S_HTML_OUT)/_static/* doc/_static
 
-$(VALIDATE):
-	touch $(VALIDATE)
-
-endif
-
-$(OUTDOC).pdf: $(OUTDOC).fo qpdf/build/qpdf
-	$(FOP) $< -pdf $@.tmp
-	qpdf/build/qpdf --linearize --object-streams=generate \
-		--recompress-flate --compression-level=9 $@.tmp $@
-
-$(OUTDOC).html: $(INDOC).xml manual/html.xsl $(VALIDATE)
-	$(XSLTPROC) --output $@ manual/html.xsl $<
-
-.PRECIOUS: $(OUTDOC).fo
-$(OUTDOC).fo: $(INDOC).xml manual/print.xsl $(VALIDATE)
-	$(XSLTPROC) --output $@ manual/print.xsl $<
+doc/qpdf-manual.pdf: $(PDF_TARGET)
+	mkdir -p doc
+	cp $< $@
 
 doc/%.1: manual/%.1.in
+	mkdir -p doc
 	sed -e 's:@PACKAGE_VERSION@:$(PACKAGE_VERSION):g' \
 	    -e 's:@docdir@:$(docdir):g' \
 	    < $< > $@
-
-doc/%: manual/$(OUTPUT_DIR)/%
-	cp $< $@