Troj/PDFex-A is a Trojan for the Windows platform that attempts to download malicious files from the internet.
Troj/PDFex-A will often arrive as a PDF document attached to an email with a subject line of INVOICE or STATEMENT.
Troj/PDFex-A will exploit a vulnerability in Adobe reader and Adobe Acrobat 8.0.1 or earlier on systems with Internet Explorer 7 installed.