If your deliverable is a .doc file along with the .pdf. some tricky scenario that can happen is, the TOC links are not functioning in the PDF output.
Here are a few pointers that may be useful in troubleshooting the problem.
Tip 1: When you insert the TOC in the word file, in in Table of contents dialog box make sure the checkbox that says “Use hyperlinks instead of page numbers” isselected.
Tip2: While saving the .doc file using Save as PDF or XPS, On the “Publish as PDF or XPS” dialog box. click Options.Select options Create bookmarks using: Headings
This adds a TOC in the PDF file under a bookmarks tab, and you can navigate seamlessly in the document.