In all of the hullabaloo about converting PPT to PDF over the last couple of weeks, I received several recommendations from people about free plug-ins that will do that for you.
Of the ones I’ve seen, the best one is PrimoPDF. When you install it, it simply becomes a choice in your printers list. So to convert a slideshow (or just about any other type of file) to a PDF, you just “print” it with PrimoPDF as your printer.