If you use one of Word's built-in heading Styles for a heading, or if you bookmark some content you want to link to, a simple cross-reference (with the hyperlink switch) can be used for the linking, though you can use a 'real' hyperlink (to bookmarks only) if you prefer. If you add the forward & back buttons to the Quick Access Toolbar, you can then use them for navigating to/from links you've accessed in the document.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]