if the word file is readable on pc, and you can make the changes trom there, try to convert back the document in PDF, OpenOffice writer has a "save as PDF document" option, or install a fake printer like
pdfcreator. you should already have a fake printer for this, installed by adobe pro. at least there was one several years ago. at this point I'd try also to convert the book in epub format with Calibre or Sigil.