Did you read that page? Herb Tyson is not given to exaggeration. He says that the Master Documents Feature remains word processing's answer to Conan the Destroyer! This is not something you want around any documents that you feel are valuable or that represent a lot of work. This feature has been known to corrupt parts of a Master Document that are not even open for editing!

Have your separate authors use documents based on the same template. Get them to use Styles for their formatting. Give them solid numbering styles to use. How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly
This advice is especially important if you continue to use Master Documents.

Look into IncludeText and RD fields.