I recently updated to Ubuntu 16.04 LTS from 14.04 LTS, and the Okular version now is 0.24.2. Now I cannot annotate certain pdf files (the "review" option is simply greyed out), which I previously had no problem annotating and viewing the annotations of.

According to "Properties" tab in Okular, the PDF file appears to be produced by Acrobat Distiller, and its "security" shows "encrypted". But apparently those didn't stop me from annotating it before. It's just some lecture slides by our lecturer.

Am I missing something to install alongside Okular? How can I annotate such a pdf file.

  • Do you have okular-extra-backends installed? This is pure guesswork; I've no idea if it will help. You might have better luck asking about this in a more Okular-specific forum, such as a mailing list or IRC. Apr 25, 2016 at 8:51

1 Answer 1


Turns out the files were DRM protected, but Okular can just choose to ignore such protection and annotate them anyways. The setting is at Settings -> Configure Okular

See https://bugs.kde.org/show_bug.cgi?id=341999

  • Just a small reminder: You need to reopen the pdf after applying the setting. Otherwise, the pdf still cannot be annotated.
    – zack
    Feb 8 at 1:45

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