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Have something like "This copy is licensed to: name, info" somewhere in the beginning of the book, around the disclaimer and other notices. Make sure it's visible enough for the person to notice.
That will stop an average consumer from simply sending it to all their friends or sharing via p2p software. That will stop the majority of sharing.
Don't worry about people who know how to extract the info from a pdf file and create a new file. If someone is willing to spend time doing this, there is not much you can do.
I'd go with PDF. Just make sure you use a font that you can embed in the document. I've seen a number of eBooks where the font was not embedded and Acrobat had to use font substitution, and then the text may not align and space properly.
And, there's nothing worse than an eBook you cannot print. If the eBook is something useful, I'll print and bind it for easier reading and reference. Only eBooks of little value (or too large) don't get printed out.
Besides, no matter what you put it into, if a person can read it, they can duplicate it. You can't completely prevent someone from copying and reproducing your eBook--you can only make it more difficult for them to do. But, you should avoid doing that in such a way that hinders your readers' use of the eBook.