There are ways to prevent it, but they are cumbersome. PDF won't do it. Unless you are REALLY, REALLY steamed, take Bob's advice. What follows is more of an intellectual exercise than a plan of action.
The Fire Department of New York got so many people swiping their image files that they implemented a cute little java script function to prevent it. Their webmaster is a lot more talented than I am. You can see his/her code at
When you right-click on the image, it says "Function forbidden - property of FDNY." For this to work you'd have to re-direct people who had turned off java script to a different page, too.
Step two would be to format your data as a images, instead of text. (The wizards here Genforum have automated this for our e-mail addresses.) You could define 800x600 images in "Paint", click on the text icon and start typing. Or, pull up your web pages locally, use CTRL + PrintScreen to copy each one as an image, paste into an image editor, trim and load.
Like I said, it is physically possible. People visiting your site wouldn't be able to enlarge or decrease the size of your text, the text would be fuzzy and you would need MUCH more space on your server. A picture really is worth a thousand words when you are renting MB's. But, no one could copy your data.