From Wikipedia:
Inf handling
Windows XP, prior to Service Pack 2
Introduction of AutoPlay.
Drives of type DRIVE_REMOVABLE do not use the autorun.inf file. Any discovered removable media are handled by AutoPlay. All other handling is as before.
XP Service Pack 2 and up (includes Vista)
Drives of type DRIVE_REMOVABLE now use autorun.inf but continue to be handled by AutoPlay. Any specified AutoRun task needs to be paired with the mandatory action key to appear as an option within the AutoPlay dialog. Otherwise the AutoRun task is omitted.
All other handling is as before.
This will allow your pdf to show up on AutoPlay but it will not run automaticly.
In autorun.inf
[autorun]
action=text
open=autorun.bat
Replace text with what you want to show up on AutoPlay.
In autorun.bat
start yourpdf.pdf
Replace yourpdf.pdf with the file of your choice.
4I'd just like to mention that enabling USB to autorun executables is a terrible security risk. Of course, I don't know your intent, just noting the issue. – Zurahn – 2010-04-23T23:48:42.250