It's already been mentioned, but I'd just like to confirm that mpdf is the easiest, most powerful and most free HTML to pdf converter out there. The sky's really the limit. You can even generate pdf of dynamic, user-generated data.
For instance, a client wanted a CMS system so he could update the tracklist of the music he played at his club. That was no problem, but he also wanted users to be able to download a .pdf of the playlist, and so this downloadable pdf had to be updated by the cms too. Thanks to mpdf, with some simple loops and interspersed variables I could do just that. Something that I thought would take me weeks literally took me minutes.
Great article that helped me get started.
