Signing a PDF file containing an image causes distortion to the image (using --clearsign).
gpg --clearsign --output='dices - signed with gpg.pdf' 'dices - unsigned.pdf'
**EDIT**: Ugh... I cannot find any means to attached files to this task!!! This is my first time with dev.gnupg.org. I guess I do not have enough rights to attach files? Please help. You can write to me at email@example.com if you do not want to pollute this task with instructions on how to attach files.
In the mean time, you can check the following site for the same bug report, but with the relevant files attached: https://github.com/xournalpp/xournalpp/issues/2962