They're also amazing for digital TTRPG sheets. You can send around the PDF form, and everyone can fill out and store their own sheet, print it, send it back to the GM, whatever the group needs.
To be clear, there are multiple kinds of PDF form. GGP might have had experience with one of those that are actually supposed to be submitted over the Internet straight from the PDF reader. (Not only is this a thing that Adobe did to their format, it is IIRC a thing that they did to it in more than one way.)
