OpenOffice's built-in PDF maker can be set to encrypt said PDF files, unlockable with a password.

Thus, should I choose to do the quarterly novella 'zine I've been playing with as a thought experiment as an e-book PDF, I can lock the files with a password only available if one pays the subscription price. Which would be lower due to lack of printing costs, etc., of paper copies.

And PDFs can work on almost anything. That's the whole point of them. Portable Document Format.

There's now a PDF reader for the new iPhone for Zarquon's sake.