Do a search on the web for "CutePDF", freeware that converts anything printable to a PDF document. How it works is it creates a "virtual" printer and adds it to your list of available printers. e.g. create a presentation in powerpoint, hit the print and choose the cutePDF printer. You are then prompted for a file name and location and that is it! Anything you can print you can create a PDF from.
If you want to go a bit further, do a search for "OPenOffice", freeware competetition for MS Office written by SUN Microsystems; apart from being fully compatible with MS Office, it also comes bundled with a PDF creator! (It is a rather large downlaod though.