Alternative to DRM?
I sometimes buy role-playing game ebooks from DriveThruRPG (as PDFs). They used to sell DRMd PDFs, but a couple of years ago moved to a much more user-friendly system, which seems to me be a reasonable balance between protecting the rights of the copyright holder and the freedom of the individual to make backup copies, lend books to friends, etc. When you download a PDF, each page is printed (very tiny at the bottom) with your name and a serial number. You can copy it, give it to your friends, etc., but if it finds its way onto the internet, the copyright holder will be able to track down who put it there.
Would this be a way out of the problems caused by DRM restrictions? What do others think?