I am sure you can transform one type of pdf file into rtf file using the "save as" menu in Adobe Acrobat. As you know rtf file is one kind of ms-word format. By one type of pdf file, I mean the pdf file is generated from text file, rather than from images, such as those of scanned books. For the later type of pdfs, you might need a software that is able to do "pattern recognition" ("word recognition" here).