checking a.pdf
PDF Version: 1.4
R = 3
P = -4
User password = 
extract for accessibility: allowed
extract for any purpose: allowed
print low resolution: allowed
print high resolution: allowed
modify document assembly: allowed
modify forms: allowed
modify annotations: allowed
modify other: allowed
modify anything: allowed
File is linearized
No syntax or stream encoding errors found; the file may still contain
errors that qpdf cannot detect