Convert PDF to PNG and back

Prerequisites

sudo pacman -S gimp imagemagick poppler

PDF to PNG

Create a directory with your INITAIL.pdf then execute this inside of it:

pdftoppm INITIAL.pdf prefix-for-images -png

Do whatever

Edit your images in gimp for example:

gimp prefix-for-images-1.png

Join PNGs to PDF

convert prefix-for-images-*.png FINAL.pdf