Adobe PhoteDeluxe Business Edition Ver.1.1 installs a PDF Writer printer driver which produces PDF from programmes which print to it. I think it has been available free on some magazine cover disks, but I can't remember which ones.
Remember that once you have written the document to a PDF file you will not be able to edit it unless you have Adobe Acrobat (not just the Reader), which as spargo comments, is rather expensive.
Also try PDF995 its free and will convert word and excel files to pdf. It opens a browser window after it has done its job and asks you to buy but apart from that there are no restictions. The pdf produced isn't as good qulaity as Acrobat makes but hey its free.