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I've been trying to encrypt a PDF document so that people wouldn't be able to copy text from it or print it. So, basically, I disabled printing and copying. I used this command:

qpdf input.pdf drm.pdf --encrypt "" pass 128 --print=none --modify=none --extract=n --

If I open it in Adobe Reader, it doesn't allow any copying, however if I use Evince, the text is easily copied. Does anybody have any ideas why?

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If people are able to view it, they are able to copy it. If nothing else: screenshot+OCR. You could try to render the text as an image before converting to PDF: then no reader will understand that it contains text, but you lose the ability to search in the document. All in all - this kind of protection is really not a protection at all, but quite a large nuisance for users. You should protect the text by another mechanism if it is important to do so, but as soon as people can read it, they can copy it. It's in the fundamental nature of information. –  Daniel Andersson Jan 30 '13 at 9:13
    
Good. If you don't want people making copies of your document, don't publish it. We should always be allowed to make copies of portions of your document for fair use purposes like archiving, translation, quoting, etc, whether it is copy protected or not. –  endolith May 24 '13 at 21:08
    
@endolith - that's actually a very silly answer that completely ignores every regulated industry out there where this is an important issue (google "controlled copies"). Such "screw you if you work in said industries" answer is a bit short-minded. –  mmalmeida 19 hours ago
    
@mmalmeida "Fair use rights take precedence over the author's interest. Thus the copyright holder cannot use a non-binding disclaimer, or notification, to revoke the right of fair use on works. However, binding agreements such as contracts or licence agreements may take precedence over fair use rights." –  endolith 17 hours ago

1 Answer 1

Easy. The "can't copy" feature of PDF's is invented by Adobe marketeers. It's not a technical restriction, nor encryption. The Adobe engineers listen to their Adobe managers and disabled the copy button; the Evince engineers don't listen to Adobe managers.

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Actually, Evince supports copy protection, but it can be turned off. I think some distros turn it off by default. See Okular, Debian, and copy restrictions –  endolith May 24 '13 at 21:09

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