Open PDF file access denied

Hi,

Two users login on a Terminal Server with the same rights.

They have the same rights on a folder.

In a subfolder are 10 .pdf files.

One user can open the 10 .pdf files.
The other user can open 5 .pdf files.
For the other 5 .pdf files he get the message 'Access denied'.

But the other person, with the same rights on the same Terminal Server (meaning the same version of Adobe Acrobat Reader) can open these files. Can open all files.

Why get the other person the error message 'Access denied' for 5 .pdf files ?

Thx