Convert epub to pdf

Does anyone know of a good program to convert epub files to pdf effectively?

I have several O'Reilly texts and have upgraded every one of them to ebooks (taking advantage of O'Reilly's excellent upgrade offer), so that I can easily search them and carry them around with me. I would greatly prefer to have pdf versions, but two of them (XML Schema and Relax NG) are not available as pdf, but are available as epub.

I have tried free online converters which did not seem to work, and it seems most everything that I can find is either not very effective, or commercial products. I am looking for something that is easy to use and free that will convert these two books. If anybody can point me out to something that would work for this, it would be appreciated.