how to reset Microsoft Word document in macbook air

Delete the problem document, and start over with a new Office document?

Check for Office patches from Microsoft?

Switch to a different text-editing and document-formatting app, whether to LibreOffice, or to an Apple iWork app such as Pages?

Nuke it from orbit?

Never heard of "resetting" a Word document. Read this then try asking again:

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Reset in which way?