You can encrypt a Microsoft Word document by giving it a password, which anyone who tries to open the document will be required to enter.

Learn how to encrypt any file in Windows 11/10 with just one click, by adding Encrypt & Decrypt item your right-click context menu.

You could always refer to Rick's guide to How to Encrypt Everything, but honestly, that strikes me as a lot of work. Instead, I recommend that you pluck the low hanging fruit: Encrypt your Word ...

In this guide we covered techniques that Windows 10 users can use to encrypt individual files, folders, and entire drives on their Windows systems.