There are three kinds of index I can think of. Let's see:
- Acrobat's index is a hidden list of words that is used to make searching faster. No way to see it on screen or a page.
- A book has an index of relevant words and terms. Selecting what goes into an index is a fairly skilled process; too large or too small is pretty useless to the casual user. An index can be created semi-automatically with a tool like Word or FrameMaker, by the author defining terms to be indexed. (Traditionally, "indexer" was a profession, quite separate from authoring).
- Some documents have automatic lists of all the words, and their count or where they appear. I believe this is properly called a "concordance". It's entirely possible to automate generating a concordance, but they are so useless/specialist that I don't know if anyone bothers to sell a PDF concordance maker.
