Doxillion Document Converter is a straightforward free-for-personal-use tool that aims to convert files between many common formats (HTML, PDF, DOC, DOCX, ODF, RTF, and TXT).
This sounded great, but did it work? We pointed the program at a folder of PDFs. This version can only convert a maximum of 5 files at one time (paying $29.99 for a licence removes that restriction), so we asked it to convert the first few - and it crashed. We tried again with smaller, simpler PDFs, and although the conversions ran to completion, the results generally bore little resemblance to our source documents.
Not a great start, then, 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 may be worth giving the program a try.