I heard on Slashdot that there is a new way to get through security by tagging viruses onto .pdf files. Has Avast covered for this yet?
as this is not new i am 110% sure they are 
New virus travels in PDF files (2001)
http://news.cnet.com/2100-1001-271267.html
PDF Virus Demonstrated (2010)
http://blogs.pcmag.com/securitywatch/2010/04/pdf_virus_demonstrated.php
Tips on Protecting Your Computer Network from PDF Viruses (2011)
http://www.brighthub.com/computing/enterprise-security/articles/76970.aspx
her are some
http://www.virustotal.com/file-scan/report.html?id=7b6b268cbca9d421aabba5f08533d3dcaba50e0f7887b07ef2bd66bf218b35ff-1303289192
http://www.virustotal.com/file-scan/report.html?id=737870d63386078cfc89459e4628ba8a0bf0cbb024019e6600a240da3e6dc9ef-1303800542
huh :-\ Well, I wonder why slashdot takes so long to tell you something… because I just found this out about a week ago…weird
do you have a link?