Have you considered using pdf files?  Or a scanned image instead of just plain old text?  It doesn't remove the problem of plagerism (people do it all the time, when I was teaching I even caught a few students doing it very subtly -- to bad I'd read the same article that day lol :).  What that will do is make it one heck of a lot harder to accomplish the same end.  They'll have to manually write out what you've said. 

 

The web is a tricky medium, and means of copyright protection are out there, but still pretty expensive... 'c'est la vie' :(

 

Mike