OK it's not a digital signature but if someone sends you a PDF to be signed and sent back, sticking a transparent PNG signature on it, and printing to a PDF that can be sent back, saves paper and time.
All you have to do is take a photo of your signature on white paper, convert that to PNG format and follow instructions on the site at https://onlinepngtools.com/create-transparent-png.
World's simplest online utility that creates transparent PNGs. Free, quick, and powerful. Import PNG, make PNG transparent.