This indicates an attack attempt to exploit a heap overflow vulnerability in Adobe Reader and Acrobat.
This issue is caused by an error in the vulnerable software when decompressing the malformed image embeded in the PDF file. It may allow remote attackers to execute arbitrary code by sending a crafted PDF file.
Adobe Reader and Acrobat 10.x before 10.0.1, 9.x before 9.4.2, and 8.x before 8.2.6
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor's web site for suggested workaround.