This indicates an attack attempt to exploit an Information Disclosure vulnerability in Adobe Reader and Acrobat.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted PDF file. A remote attacker may be able to exploit this to gain sensitive information from vulnerable systems, via a crafted PDF file.
Adobe Reader XI (11.0.11) and earlier 11.x versions
Adobe Reader X (10.1.14) and earlier 10.x versions
Adobe Acrobat XI (11.0.11) and earlier 11.x versions
Adobe Acrobat X (10.1.14) and earlier 10.x versions
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.