UPDATE 2025/10/24: After the suggestion to try MS WORD WEB, I've refined the results as follows:
2 MS Word Documents: 1st: 2100 pages, 16MB, 2nd: 1700 pages, 12MB
With NO hyperlinks in TOC:
- MacOS: both documents can be exported to PDF with no issues
- Windows/PC: both documents can be exported to PDF with no issues
- Word WEB: Export works for smaller (e.g. 1/2) document, fails to open for 2100 page document - still doing tests to see what size works
WITH hyperlinks in TOC to headers IN SAME DOCUMENT (no hyperlinks to external docs):
- MacOS: export to PDF of both documents fail around 650 pages in size (error indicates "internet problem"
- Windows/PC: no failures during export to PDF
- Word WEB: failure of PDF export fails at 1292 for first document - still have to test 2nd document

I'd say this is not necessarily a "Mac issue" exclusively but clearly Word for Mac appears to be doing something different for export to PDF that Word for Windows is not.

I feel like this is not a one off situation as I've seen multiple postings in various forums about this and similar issues but haven't seen any clear resolutions (other than making the document smaller which would be problematic as this goes from a 2 volume set of documents to 4+ documents).

Wondering if anyone else out there is currently seeing this issue - in particular on MacOS for files this size with hyperlinks in TOC.
Thanks