Doxillion Document Converter is a straightforward tool that will quickly convert files between many common formats (HTML, PDF, DOC, DOCX, RTF, and TXT, with the ability to read - but not write - WPD files).
This sounded great, especially for a (currently) free tool, but did it work? Well, not always as you might hope. We pointed the program at a set of PDFs (it can run batch conversions of entire folders, when necessary) and it crashed. We tried again with single PDFs and it either extracted just the title page, or, more normally, completed the document but left out all the images.
Not a great start, then, even by beta standards, but when we tried simpler documents the results were significantly better, with the program quickly and accurately converting a series of plain text DOC, DOCX and RTF files to PDF.
And so while we wouldn't recommend Doxillion Document Converter for use with lengthy or complex documents, if, say, you just want to convert some text-only DOCX files to HTML or PDF, then it's definitely worth giving the program a try.