In post #2 I asked whether the fonts concerned are installed on the other computer. Given that you've now introduced a Mac into the scenario, are you sure the documents use only Microsoft fonts? If not and the faulty display is related to such non-Microsoft fonts, you have two choices:
1. Use only Microsoft fonts; or
2. As indicated in post #2, embed the fonts in the document (font license permitting).

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

The documents in question were not created on my Mac computer. And these same documents open correctly on my Windows 10 PC as well as on my Mac.

Some of the problematic documents (for my client but not for others) were created on his own PC, and others were created by other Microsoft Word users, including the one I attached from the University of California, Berkeley. This particular document opens fine on both my Mac and PC.

My client has no control over how Word documents are created by others who send them to him. Since I can open these documents correctly on both a Mac and on a Windows PC I have to conclude that there is something wrong on my client's computer.

Unfortunately, figuring out what is wrong and how to fix it has proven to be very difficult. I appreciate your help and trust that you and/or others can offer more suggestions.