I'll give the full Acrobat a couple props over PrimoPDF. It plugs itself into Word, Excel, and PowerPoint and does a couple things better than the printer drivers. It will notice URLs and the the resulting PDF will be hyperlinked. It will also notice "goto" buttons in PowerPoint, along with some slide transitions, and reflect those into the PDF as well. Most importantly, you get corner-to-corner PDF from your PowerPoint, versus the apparently inescapable half-inch white margin that you get through the normal printer drivers.

Of course, for a student submitting something to a professor, PrimoPDF would be just fine.