I authored a 450 page textbook (*.indb file, CS6) and am creating a separate companion workbook for use with the textbook. I would like an index or content outline in the workbook to reference pages in the main textbook (so I can regenerate the workbook index when changes are made in the textbook). Is this possible, and if so, how do I do this? Thank you.
Yes, you can do that indeed.
As you are already using an InDesign Book file. You can add the companion workbook InDesign file as the last file in the Book panel. This document can have its own document page numbering, making it part of your book allows you to generate either an Index or a Table of Contents that is sourced from the rest of the publication.
Hope this helps,