Which copy protection techniques are available for digital material?

Question

Suppose a website offers the following resources for premium users:

• PDF Files
• Video Files
• Presentations (e.g. .ppt files)

Which protection techniques are available to prevent (slow down) the user to copy and re-distribute these resources?

Answer 1

PDF - password protection

Video files - DRM (unable to play without license file)

Presentations? No idea.

Most these techniques are also sure techniques to repel normal users from your site.