If you create a bookmark or hyperlink anchor
in an InDesign document, you can cause a button to jump to that
anchor, even if it’s in another InDesign document. Use the Bookmarks
panel and Hyperlinks panel to add anchors.
Note: If you specify an anchor in a different
document, remember to export that target document to PDF, and use
the same filename as the InDesign document, replacing the INDD extension
with PDF. Also, store the PDF documents in the same folder to make
sure that the links remain valid in Acrobat and Reader.