I'll keep this general, because I really can't argue with the statement "Microsoft Office shall be used." Such a requirement ends all discussion, as far as I'm concerned. So I'll make some general statements and perhaps you can make use of them.

I've done a little documentation on over the years, versioned in cvs and later perforce.

Text changes. For text, you need a mergable format.

Tables change less often. Best to have it there too. If you can generate the tables from a versionable text format, that's ideal.

Graphics don't change much, in my experience. (Generated graphics do, but in those cases it's better to store the source, of course.)

If you can find a way to split your documentation into text-only and graphics-only files, you may find that the text files merge easily and the graphics files don't present much of a problem. When graphics files need merging, they often need human attention anyway.

Can you do that?

Arnt