...the PDFs are straight spam replacing the 'images' popular in all the stock tip mail from q1, while the greeting cards are leading you to a site that will attempt to install a bot on your computer.  You should be safe as long as you keep your updates current.  Both are very hard to filter for (which explains why they are so popular with spammers now) ...

 Report on email threats: massive botnets spread PDF and malware
Posted on 18 July 2007.

Commtouch released its Email Threats Trend Report for the second quarter of 2007, based on the company’s real-time analysis of billions of email messages globally each week. Highlights include:
 
• Spam with PDF attachments was initiated at the end of the second quarter. During one massive attack, PDF-spam comprised 10-15% of global spam messages during a 24-hour period, increasing overall global spam traffic by 30-40%
• Spam and viruses have joined forces, using the same botnets to distribute both types of email-borne threats, sometimes even in the same email message
• Global spam levels remained high; 85-90% of all global email is spam
• Over 60% of spam-sending bots also send malware
• Over 300,000 zombies become newly activated each day
• Image spam in Q2 dropped to less than 15% of all spam, compared to 30% in the first quarter of 2007

Spammers unveiled a new email tactic toward the end of the quarter: PDF spam. This type of spam aims to evade anti-spam filters by disguising itself in a common format: attachments of the familiar Portable Document Format files. This trick helps the junk message pass many anti-spam solutions since it looks like a legitimate email.
 
More details, including samples of PDF spam and spam messages containing malware, are available in the Commtouch Q2 2007 Email Threats Trends Report