You can have someone convert them for you that is a registered user - nothing
cheaper than that I can think of.
Acrobat is well worth the price and if you can find Version 4.0 (the latest)
for $180.00 it would be a great deal.
One of the nice features is it's ability to save HTML websites and download
(and preserve) all links. Therefore, if you want to review a website offline,
you can go to the site and print it to the PDF driver. It will "snake" its
way through all of the links and save all sites within a set number of levels
that you choose. When viewing the sites, you can launch any of the links that
are outside of the pdf pages saved.
If you own Pagemaker, Acrobat distiller is included and you can create PDF
files with it. Outside of these suggestions, there is no other way that I
know of to convert to PDF from another format.