It should be relative link, not an absolute one. That's because you don't know which drive letter will be assigned by the PC that reads it.
A point to note: not all PC's have a pdf-reader installed. So you should provide that on your CD, and have a way to have the user install it. It's your choice if you provide the full install file on your CD (you should have permission for that from Adobe or Foxit or whatever company that makes the reader you provide) or just a link (but the user need Internet connection then to get it).
Here is what I want the CD I am selling to do:
1. AutoRun (I have the basics of an AutoRun.inf file)
2. The autorun opens a PDF file
3. The PDF file is a Table of Contents page
4. The PDF Table of Contents on the CD links to other PDF files on the cd
How do you burn the initial CD (going to the duplicaters) so that the files point to/link to files on a CD?