This indicates an attack attempt against a remote code-execution vulnerability in Adobe Reader and Acrobat.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted PDF file. It allows a remote attacker to execute arbitrary code.
Adobe Reader 9.3.2 and earlier versions for Windows, Macintosh, and UNIX
Adobe Acrobat 9.3.2 and earlier versions for Windows and Macintosh
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch from the vendor: