I use masterpdf editor, the 4.x open-source version vs. newer non-opensource 5.x versions (ie. different packages), it works great for signing/editing pdf's for like past 10 years to avoid print/sign/rescan bs. It was always free prior before 5.x for linux users (pay up windoze/mac slaves), but now they charge unilaterally in new versions.
First, take a photocopy scan of your best signature, import into gimp. Do an alpha transparency on it to remove the background leaving only a clean signature overlay, save as a transparent png file preserving the alpha layer. Import the image using masterpdf editor or other to just apply over in the pdf, and save a copy of the file as pdf again to send back. Haven't had to do this in years, but google "gimp alpha transparency layer" and use the magic wand tool as your friend to do so, not terribly difficult.
This saves me much sanity dealing with signing documents over the years for various customer and legal docs, and allowed me to be rid of using my mfc printer/scanner long ago (though now I use it more as an ottoman under my desk still). Masterpdf is pretty dope, it's like $70 bucks, I should probably buy a compulsory copy in thanks
regardless after all these years vs paying for Adobe Acrobat, but the old warezer
in my says meh, go free.
-mb