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.

PDFs can be container files, which hold files in other formats. Javascript, used to automate tasks in Acrobat is not considered to be a secure scripting language. Most anti-virus software cannot pick up on malware embedded in PDFs.