The fact it's PDF files is of little consequence. It's bootlegging. If it became popular, you would get raided for distributing copies. It doesn't happen for small-scale transfers between friends but if you start doing it on a large enough scale then you're asking for trouble. People have had similar ideas since recorded media has existed. Pirate copies of CDs, books, movies, etc. are sold freely in countries where IP laws are lax, and generally not sold in countries where these laws are enforced. The risk of getting caught could be lowered quite a bit by taking precautions, but if you're actively trying to be a large-scale pirate then you're bound to run into trouble eventually. Enforcement is focused on distributors rather than consumers usually. But with AI and increasingly invasive tech, that could change.