A few weeks ago I needed to print some large documents to PDF format, but I didn't have anything installed to be able to print to PDF. I so rarely need to print to PDF that I've never been able to justify buying software for this.
A friend pointed me at www.pdf995.com. They have a free/sponsored program for download to be able to print any document to PDF. It works quite well and you only get ads on your screen when you print something to PDF. Works for me! You can choose to buy the software for, you guessed it, $9.95, and the ads go away... but I haven't purchased yet.
Per the comments on this blog, I have switched to PDFCreator.