Question: Version of Word? It is important.

In the meantime, "section" is Word jargon and may have nothing to do with what you are asking. Sections / Headers and Footers in Microsoft Word (Ribbon Versions)

Here are some resources on letter templates:

• Setting Up Letter Templates - Ribbon by Suzanne Barnhill, MVP
• How can I get a different header/footer on the second page?
• Letterhead Textboxes and Styles Tutorial

In recent versions of Word you can simply restrict editing - no changes with exceptions. If this is done, the headers and footers are not exceptions. You should be familiar with the StyleRef Field which is demonstrated in the third link.