How do I script Powerpoint to save a directory of PPTX files as PDFs?
Assuming you have PowerPoint installed, this is quite simple using Automator.

(I have Office 2011, so I'm unsure if this would work with 2008)

Start Automator, and create a new Folder Action, and choose the input folder (i.e.: the one containing the PPTX files)

From the Actions list, choose "Convert Format of PowerPoint Presentations".  For the "New Format" option, choose "Portable Document Format".

Save it &amp; close Automator, and you're done!

Any PPTX files saved in the chosen folder (either pre-existing, or any new ones you save from now on) will automatically be converted to PDF as an additional copy.

Hope this helps!

-U