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.