OpenOffice 3.0 is in beta, but it has a new PDF import capability, see
PDF import and Hybrid PDFs as a new extension. Unfortunately, it "favors layout over editing" and so imports into Draw rather then Writer. The code is LGPL v3, and so could be used in alternative converters. Perhaps more interesting is hybrid PDF output. This is a PDF with ODF (OpenDocument Format) embedded in it, so I assume at a minimum it reflows and could be cleanly converted to RTF. If this format becomes common, some of the disadvantages of PDF might be mitigated.