I am implementing 2008 right now and ran into an interesting problem. When plotting to PDF by layout tab in 2008, everything including the plot preview looks great, but the final PDF was be shifted to Up and to the Right. I found a thread on the discussion Groups recommending that you (first back it up) replace
C:\Program Files\AutoCAD 2008\Drv\pdfplot9.hdi
C:\Program Files\AutoCAD 2007\Drv\pdfplot.hdi.
Make sure it is the updated version from Service Pack 2 dated 3/22/07. This seemed to solve the problem for most after a reboot. I still had the same problem and found in my case it was because I made make the printable area on my PDFs the entire sheet. I plot to the edge of the paper, which PDF is not liking in 2008. I created some new sheet sizes bringing the edges of the printable area in, and everything started working again. I'm guessing that how far you will have to bring in your edges may vary, so start with a big number to see if it's working then start working your way back to see what you can get away with.
On a related note, I also came across this system Variable "publishcollate". It toggles your print to DWF from single to multi page DWFs. Handy.