This software can convert XML files to PDF and a variety of other document files.
One great thing about FOray is that it's been written in Java 2 Standard Edition Version 5.0. This means that it can be used for both embedded and standalone applications. This versatility could be exactly what you're looking for, especially if you need to use this software in a variety of situations.
All in all, FOray is certainly worth checking out if you're in need of an XSL-FO publishing system. Its open-source nature should be appealing to anyone, and the fact that it can handle so many different document formats is a major plus. It's not perfect, but it's definitely worth considering!
Version 0.3: N/A