[nanobit]

One of my friends wrote an ebook in PDF format and wants to distribute it on CD. I wonder how it can be protected from illegal copies.
the first thing came to my mind was: wrapping in with a self-written code and activating online, but this method requires a lot of coding and having a dedicated server. the next I thought about was using a commercial CD protection which makes copying the CD itself more difficult. the time I was into these things one of the famous one was Laser-Lock.

so guys, do you know any good CD protector for this case? I want to know your opinions about it. any practical suggestion is appreciated :-)