If you google for "freeware PDF creator", believe it or not, you get almost 3 million results! Many of the PDF tools are free (as in beer), such as CutePDF, PDF995, Go2PDF, PDF4Free, etc. Yea, it's not difficult at all to locate a free PDF tool, the real challenge is which one is the best?
My vote goes to PDFCreator, a free tool for creating PDF from any Windows applications. It is installed as a virtual Windows printer. It supports PDF encryption for both 40- and 128-bits! It can merge multiple files into a single PDF. As well, it's under GPL so it's 100% free for both home and commercial use!
The tip from me is that in order to create the highest quality PDF files with lossless pictures, you can change the image compression algorithm from "JPEG" to "ZIP", and down sample the resolution to "120". This resolution is generally good enough for distribution.