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When encrypting a PDF in Adobe Acrobat Pro XI, there's a message to the effect that some third-party programs which read PDFs may ignore the encryption password and open the PDF for viewing. Is Adobe PDF encryption really no more than a sign on a door that reads

This door is locked. The key is in the lock. But don't use it.

??

All Adobe products enforce the restrictions set by the Permissions Password. However, not all third-party products fully support and respect these settings. Recipients using such third-party products might be able to bypass some of the restrictions you have set.

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  • This seems like a good question to ask in the chatroom. There are tools that can read a encrypted PDF file
    – Ramhound
    Aug 13, 2016 at 10:42
  • Do they have to "break" the encryption, or is the password visible to them?
    – TRomano
    Aug 13, 2016 at 10:43
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    I believe that ignore the encryption password simply means that those applications will try to display the file and will end up displaying crap. So it's telling you that by using encryption you are effectively making the file impossible to use for applications that don't support encryption.
    – Bakuriu
    Aug 13, 2016 at 10:43
  • @TRomano - Depends on the restrictions placed on the document by the program which created the document. A program can ignore the restrictions to print or copy the document. A program would have to brute force the password if its protecting it from being opened.
    – Ramhound
    Aug 13, 2016 at 10:44
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    Note that you can have pdf files with a password but without encryption. In that case other applications can just ignore password. However if you encrypt the document, there is no way to open it without entering the decryption key (i.e. the password). There are also authorization passwords (e.g. ask a password to print the document etc) and those can be bypassed by 3rd party tools.
    – Bakuriu
    Aug 13, 2016 at 12:39

1 Answer 1

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If you add a password to view a PDF, then the file is actually encrypted. There is no "honor system" - any program will have to have the password, or somehow crack the security, to view the file and edit it in any way.

If you add a password to control any other functions, such as printing or editing, then the "honor system" is in effect - while Adobe products and most other big-name PDF readers will honor these restrictions, there is nothing preventing a program from just ignoring them, and nothing preventing the user from simply opening the PDF in a text editor and removing the "restrictions". Hence, the reference in the message to a "permissions password".

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