I’ve received several PDF documents lately that would only open in Adobe’s Acrobat Reader without being asked for a password. In Acrobat Reader, the document is then usually ‘protected’ against printing, annotation and/or other things one does with a PDF. Unfortunately that doesn’t help me much because I won’t install the closed source Adobe Reader on my notebook. No way.
But here’s a quick fix: Files that Evince and Okular can’t open can still be viewed with the Firefox PDF viewer. Nice, but it’s still a major pain. So I spent some time to see if this annoyance could be removed. And indeed there is a simple solution:
To remove what is referred to as ‘owner protection’ with an empty password, use ‘qpdf’ in a shell:
qpdf --decrypt in.pdf out.pdf
And that’s it, no password required. After that, the PDF file can be opened in Evince and Okular and has no restrictions on what can be done with it, including printing it, modifying it, etc.
Qpdf also has a command line option to show which actions are ‘not allowed’ when an empty owner is set password:
qpdf --show-encryption in.pdf R = 6 P = -1084 User password = extract for accessibility: allowed extract for any purpose: not allowed print low resolution: allowed print high resolution: allowed modify document assembly: not allowed modify forms: allowed modify annotations: not allowed modify other: not allowed modify anything: not allowed stream encryption method: AESv3 string encryption method: AESv3 file encryption method: AESv3