I think it's safe to say that since nobody answered this the first time you posted, or after you bumped it, nobody has any ideas.
Well, you could combine all the documents into a single document, with Pages (panel menu) > Move Pages...
Thanks John, I think I'll aim to do the linking manually in Acrobat once it's been exported, but I may look to combine them as a simpler option going forwards.
I have 8 documents in a book, all of which share a common footer area that I want to act as a navigation bar across all chapters. The idea is that a user with the book PDF can click on a chapter number in the nav bar in the footer and go straight to the relevant place. I can create a TOC across the whole book, but I can't find a way to set the links in the footer of each document to the relevant pages within the book, and have that be common across all documents.
Any thoughts on how this can be done?
Have you tried creating a cross-reference for each chapter in the master page footer? Converting the x-ref to text, in each chapter file that points to itself, avoids having that x-ref appear as a live link when hovered over.
Search Google for terms like "InDesign cross-references," "InDesign cross-references between files," "InDesign cross-references in exported PDFs," "InDesign synchronizing books," without quotes, for links to discussions.