How to sign a PDF document with an image instead of and without printing and scanning
Xournal++
https://github.com/xournalpp/xournalpp
Well maintained, available for debian with sudo apt install xournalpp
A little bit clunky, need to select the tool and then press each time, no right-click menu available.
Also every time an image is moved a copy gets left behind? Yikes. But the object select tool lets those get deleted.
Or maybe if i switched from the image tool to some sort of move tool it would have worked more as expected.