Hi 
So you want something like "Captcha" as found in many websites but
want it for normal documents? I'm not sure how to do that at all.
Hopefully someone else might. My 4 thoughts would be;
1. Could the documents be stored on an intranet? Errr, i mean on a
website that can only be accessed from inside the university
buildings? (maybe also by people who are allowed access from outside)
2. my other thought is to have a website that people have to login
to. Perhaps different areas within the website so 1 area for physics,
one for engineering, another for arts. Each area could have a
different group of users with their own individual passwords.
3. Some sort of Cloud arrangement for sharing files where individual
files can only be accessed by specific people people invited to look
at a certain file?
4. Have you heard of "moodle"? Maybe something that already exists
might be able to do what you want already.
As i said i hope someone else has a better idea
Regards from
Tom 