There is the whole watermark technique for paper documents. The same kind of technique certainly exists for electronic documents. But once you add components to limit access to the documents, you have to use much more sophisticated technologies that call for infrastructure and investment, and place a lot of access restrictions on members.
How far do you want to go to guarantee security? I will never be able to guarantee 100% that there will be no malicious intent on the part of someone who decides not to follow the rules.