SUMMARY It would be handy to use OpenPGP certificate to sign a PDF document. Why ? Because Kmail creates automatically an OpenPGP certificate to sign the email when creating an account. LibreOffice can use the OpenPGP certificates created by Kmail. Thanks
Hi This is not specified in the pdf specification, so it would be a purely okular-to-okular feature. While it probably wouldn't be many man weeks of work to implement something that works, given it is not actually specified in the pdf spec, I don't think it is useful.
Ok In this case, it would be a good thing that Okular, at the first opening, creates automatically an S/MIME OpenPGP certificate with Kleopatra.
(In reply to Philippe ROUBACH from comment #2) > In this case, it would be a good thing that Okular, at the first opening, > creates automatically an S/MIME OpenPGP certificate with Kleopatra. In general, S/Mime (x509) certificates needs to be authorized/notarized by a 3rd party (not unlike how browser https security works), so just generating something is not going to be useful in the long run. For example, in certain countries, you can get a governmental issued certificate with a government organization as trust anchor.
We're not going to do that. An okular only feature is not useful, and a self signed certificate is not useful. For that level of not actual cryptographically-valid signature you can as well just add a stamp annotation with your signature as an image and call it signed, that's what most people want anyway ¯\_(ツ)_/¯