You rename a chapter, add a section and move several pages. The body is correct, but the contents page still leads readers through the old version. An automatic table of contents may need an explicit update after those edits.
Check the structure before refreshing it
For an ordinary Word document, use the intended heading styles for chapter and section titles. Making text larger and bold is not the same as assigning a heading level. In Word for Windows, the Navigation pane helps inspect headings in the main body. It does not list headings inside tables, text boxes, headers or footers, so an absent entry there is not a complete diagnosis.
In desktop Word, right-click the automatic contents field and choose Update Field. When offered a choice, updating page numbers only keeps the existing section list. Choose the entire-table update after adding sections or changing headings. If the contents page was typed manually, it is ordinary text rather than an automatic field.
Inspect a small route through the document
For example, rename “Preparation” to “Before you start” and add a short section in a working copy. After updating, check the new wording, the added entry and an unchanged chapter near the end. Follow the links and compare the displayed page numbers with the actual destinations.
Save the source and export a fresh copy. Open the file you are about to send, not an older PDF left in Downloads, and repeat those checks. Keep source and export together with an identifiable revision so the next edit starts from the right document.