SUMMARY *** I am attempting to add PDF digital signatures by following https://rajeeshknambiar.wordpress.com/2022/06/27/digitally-signing-pdf-documents-in-linux-with-hardware-token-okular/ The digital signatures option is not available in PDF Backend Configuration, only "Enhance thin lines". I have removed Okular using apt and reinstalled to Version 20.12.3 using snap. I have also installed Poppler 21.09 by following https://askubuntu.com/questions/1240998/how-to-install-poppler-0-73-on-ubuntu-20-04-any-change-since-18-04 *** STEPS TO REPRODUCE 1. Install Okular 20.12.3 using 'sudo snap install okular' 2. Open Okular > Settings > Configure Backends 3. Select PDF Backend Configuration OBSERVED RESULT Only "Enhance thin lines" option is available. EXPECTED RESULT "Certificate database" option should also be showing, as in p. 35 of https://docs.kde.org/stable5/en/okular/okular/okular.pdf SOFTWARE/OS VERSIONS Linux/KDE Plasma: Linux (x86_64) release 5.13.0-52-generic KDE Plasma Version: 5.18.8 KDE Frameworks Version: 5.68.0 Qt Version: 5.12.8 ADDITIONAL INFORMATION I'm fairly new to Linux so I'm sure I've made a mistake somewhere! Any help is greatly appreciated, thanks.
> I'm fairly new to Linux so I'm sure I've made a mistake somewhere You have, don't try to compile stuff if you don't know what you're doing. My personal recommendation is that you use Okular from flathub if your distribution doesn't provide one recent enough. https://flathub.org/apps/details/org.kde.okular
Flathub, got it. Thanks very much for your help!