Huh. "Signing" PDFs in one way or another is old hat, like for 25 years now. And FWIW since PDFs are electronic files, you can acknowledge and sign them with a digital signature (certificate) which has been accepted and sanctioned under Federal law since something like the Reagan administration. (Yes, that long ago, and folks still don't know how to use the tools to do it.)
Of course with a Samsung Note and some other non-Mac tablets, you can literally sign any "form" that you display on the screen
, with the stylus, and the tablet will incorporate it into the electronic file.
Not much new here.