The control for Adobe Reader 5.0.9 and 5.0.10 on Linux, Solaris, HP-UX, and AIX creates temporary files with the permissions as specified in a user's umask, which could allow local users to read PDF documents of that user if the umask allows it.
http://www.redhat.com/support/errata/RHSA-2005-575.html
http://www.adobe.com/support/techdocs/329121.html