bullzip.com produces a series of products, some free, some pay per licince, for Windows PCs. Two of these products, PDF Printer (free up to 10 users) and PDF to Word converter work with PDF files on Windoze. PDF Printer isn't needed on a Mac and PDF to Word seems to create editable forms of PDFs. In theory it should be possible to convert a PDF to a MS Word document and then "print" the changed document back to a PDF using PDF Printer. A trifle long-winded but it should work.