I really don’t know how you could prevent someone from copying your pdf’s. You can protect the PDF within Acrobat from having people cut and paste your text. Maybe you can even password protect them. You can even password protect the files on the CD. But if someone really wants to steal your text they sure will. Even if you could prevent the PDF’s from being distributed, anyone could either copy down the text right off the screen, they could take a screenshot, and possibly OCR that, or just use the images, or even print it and OCR the printed pages. If someone sees it they can copy it. Period.
Heck, it’s even possible people might read it, remember it, improve on it in their minds and write their own PDFs which will be based on your writings in their essence but will be improved and expanded. Who knows, maybe your own writings are based on someone else’s–maybe you don’t even remember where these ideas got into your mind. But that’s how civilization advances. People put ideas out there and others take them to the next level. If you don’t want to risk someone “stealing” your ideas, just keep them to yourself.
Just think how much of what you see and read out there is so similar with variations on the same themes? Movies, books, music, art, software…