I run 18.04.1-Ubuntu and have installed okular using snap
okular 19.04.2 63 stable kde✓
I'd like to create image signature stamps with okular like described here
I successfully added an image signature to my pdf document, and can save and reopen it with okular without problem.
Unfortunately no other pdf viewer on my system. Neither Evince document viewer (3.28.4), nor Atril Document Viewer (1.20.1), nor Xournal (0.4.8) see the signature. This does not seem to be a problem with my signature image, all the other default stamps I have tried are not seen by other viewers.
Is there any way that okular can create these stamps in a way other applications can see them? Note that I tried printing to pdf but this does not work as explained here