PDF Index Generator is a powerful indexing utility for generating the back of your book index and writing it to your book in (4) easy steps. PDF Index Generator parses your PDF, collects the index words and their location in the PDF, then writes the generated index to a PDF or a text file you specify. The main target for PDF Index Generator is to automate the process of generating the book index instead of doing the hard work manually.
I didn’t get to try this out, but I had it bookmarked. (UPM was very kind to do the indexing for me since the moment it needed to be done was also the moment that my father died.)