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'
File signed with distorted image.
Original file, unsigned and undistorted.
PNG used to create the unsigned file. Comes from Wikimedia, so it is ok to distribute.
Blank PDF used to add the image //dices.png// to.