How do I find the exact encryption on a PDF file? I can't seem to get a direct answer on the net. For example how do I tell if a document is PDF 1.1 - 1.3 (Acrobat 2 - 4), PDF 1.4 - 1.6 (Acrobat 5 - 8), PDF 1.7 Level 3 (Acrobat 9), or PDF 1.7 Level 8 (Acrobat 10 - 11)? Additionally does anyone know which version Microsoft Word 2013 would use when I encrypt the file with a password?

closed as off-topic by schroeder, Mark, this.josh, Eric G, RoraΖ Apr 8 '15 at 11:16

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about Information security within the scope defined in the help center." – schroeder, Mark, this.josh, RoraΖ
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If you know the password to the file, you can view the encryption type using Adobe Reader. Go to File -> Properties -> Security and click the "Show Details" button. See 'Screen Capture 1' below. The security tab will also show you what version of Acrobat can open the file. See 'Screen Capture 2'.

As shown below, MS Office uses 128 bit RC4, which is insecure, unlike AES encryption, and should not be used.

Screen Capture 1 Screen Capture 2


From wikipedia, the latest versions of MS Office use 128 bit AES encryption.

As for the PDFs, this Adobe link shows the Acrobat and PDF version, stating,

Sets the type of encryption for opening a password-protected document. If you choose Acrobat 3.0 And Later (PDF 1.3) option, a low-encryption-level security (40-bit RC4) is used. If you choose Acrobat 5.0 And Later (PDF 1.4) or Acrobat 6.0 And Later (PDF 1.5), a high encryption level (128‑bit RC4) is used. Choosing Acrobat 7.0 And Later (PDF 1.6) encrypts the document using the AES encryption algorithm with a 128-bit key size. Acrobat X And Later (PDF 1.7) encrypts the document using 256-bit AES.

And if you want more information, this wikipedia article is highly detailed.

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