OMG WTF PDF
Beware of the security flaws of the PDF format. As detailed by Julia Wolf, a senior security researcher with FireEye, in her presentation OMG WTF PDF: PDF Ambiguity and Obfuscatoin, PDFs are often used in malware attacks. See the video here and the slides here. A PDF can contain a database scanner that gets activated when the file is printed. PDFs can also be manipulated to display different content in different PDF editors or different web browsers.