[Files] Ability to Restrict PDFs from being downloaded by students.

[administration2]

Problem statement:

We need the ability to restrict students from downloading PDFs in their courses. Many of these PDFs are purchased and licenses per user. Giving the student ability to download and distribute violates this.

Proposed solution:

Give admin the ability to turn this feature on for teachers to control

User role(s):

admin,instructor,ta,designer