Some PDF viewers (e.g., Preview, Okular) let you place images of your signature on a document and then export the "signed" version. I haven't had issues with getting these documents accepted.
None the less, a company the other day insisted that I print out a form, sign it, take a picture of the signed form and send them that. It was almost enough to bin them off, but unfortunately I was deep enough in the bureaucracy by that point that sucking it up was less hassle.
convert -density 130 input.pdf -rotate 0.33 -attenuate 0.15 +noise Multiplicative -colorspace Gray output.pdf