Not sure if anyone ever used it, but there's simple HTML to PDF converter sample in C# done with iTextSharp on code project at http://www.codeproject.com/KB/cs/pdfizer.aspx.
The iTextSharp (http://itextsharp.sourceforge.net/) is a free PDF generator API, ported from the free Java iText PDF generator library. So there's possible the Java version too.
It sounded a simple enough way of doing what you want.
Check it out, and feel free to provide feedback or even upload a solution with it.
Miguel Simões João