How to document in a way that can be easily merged with coworkers revisions?

We use word documents with pages and other things that get in the way of merging.

So if developer 1 works on code A and updates word document A but developer 2 checks in code B and document A before. Then it’s painful for developer 1 to resync document A

I’m wondering if anyone is aware of a more ideal resolution. How can we efficiently merge word documents, or what alternative that is acceptable in high compliance area where documentation had to be updated before code would use?