PAF can create your book in MS Word (or whatever your default program is for opening RTF files). Instead of clicking on Preview, make sure there is a checkmark in "Print to file" and click on "Print".
It will open a "Save as" box, where you give your file a name and a location. Then (at least on my computer) the file opens in Word, and I can do some fine-tuning such as resizing photos, and minor edits.
To add an index, click Ctrl+End to move to the end of the file, then Ctrl+Enter to add a page, and then insert an index (the exact steps for inserting an index depend upon the version of Word you have).
Then save the file in Word format to keep it from opening in Wordpad.