OSX's Preview allows you to import your signature by writing in on a white notecard or similar and holding it up the webcam. It then stores a vectorized version which can be added to PDFs.

Caution that a vector graphic could look too clean in some situations. Clearly an issue per the OP.

See my note above re blurring the lines a little in Photoshop.

Thanks for this tip! Preview has evolved so many little features the name is borderline misleading at this point.

I did it once with GIMP, and apply it every time with xournal. In my experience people do not really require that the PDF looks printed and scanned, so I never cared about that aspect.

+1 for xournal, and I can anecdotally confirm that this has never been a problem for me for a decade.

Same. Has always worked.

I found this GIMP tutorial several years ago and have used this method ever since. I insert my signature into PDF documents using the stamp tool, unless the software has a more sophisticated method.

https://www.youtube.com/watch?v=efAOsvfi4sU

I scanned a signature and set of initials, traced them in Illustrator to neaten them up, colored the ink blue and blurred the lines a little in Photoshop, then saved with transparent backgrounds in a couple of formats. PNG and TIF are the ones I mainly use.

In my ancient version of Acrobat I created rubber stamps from the PNGs. Two clicks to drop them in, a quick resize and adjust the placement, and Bob’s your uncle. Never need a pen again.