Rivits
If you're using an old version of WP, then you are limited in terms of what you can do. You can't usefully try to convert them to another format with a better typesetting engine - stuff would go wrong in the transfer
Best to simply install either CutePDF or PDFCreator and simply print to that, that should generate the PDFs OK
CutePDF Writer
CutePDF - Convert to PDF for free, Free PDF Utilities, Save PDF Forms, Edit PDF easily.
PDFCreator
PDFCreator | Free Business & Enterprise software downloads at SourceForge.net
as I said before - both come with bundled junk, so untick the boxes