Any help appreciated and thanks in advance.

Go to www.onlinedocumentconversion.com upload your PDF pages, convert them to rtf & then edit them! If you have any difficulty, contact their ‘After Sales Support & Service’ team – they are a bunch of friendly and helpful folks & I am sure you will like taking their help.

What owlwings said. TIFF is a graphics format. I've never heard of a book being formatted as a graphic. But maybe the author set it up as a TIFF to try to keep it from being pirated. Also, I wonder why you feel the need to change what was written. Unless you wrote the book, you have no right to make any changes in it. The author is the only one who can legally change it. If you disagree with some of what it says, just don't pay attention to those parts.

A TIFF is an image file. It is not a word processing document so you cannot edit it to change the text. The most practical solution would be to use Optical Character Recognition (OCR) software to 'read' the pages and to convert them into text. You would have to do this page by page if each page is a separate image file. There is a list of free OCR software here: http://www.freeocr.net/ You may have to try more than one to find the best solution for you.