I can't find a free/open-source software that password protects my PDFs with AES 256.

pdftk just offers 128-bit strength.. In fact I didn't find any other tool that encrypts PDFs.

What tool may I use to password protect my PDFs, using AES 256

  • Why not use pgp or openssl or other? Oct 9, 2015 at 14:26
  • Because I require a password protected PDF, using AES 256 Oct 9, 2015 at 14:36
  • 1
    You mean, because you need it to be compatible with Acrobat? Because you haven't specified that as a requirement. Oct 9, 2015 at 14:39
  • No, simply because I need a password protected PDF, as stated in the OP. I will be using these PDFs for encryption test and other similar projects.. Oct 9, 2015 at 14:41
  • I understand what you want. I'm just trying to point out that a pdf encrypted with another utility would still be a password protected pdf. Just not the kind you are looking for. Oct 9, 2015 at 14:42

1 Answer 1


QPDF says it supports 256bit encryption in it's massive manual. I didn't read it all and have never tried it. It looks like it's worth a shot.


  • Just tried it out, works a treat!
    – sxc731
    Jul 22, 2016 at 16:20

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