As far as I know, Word doesn't record the names of everyone who edited the document but it does track a couple of them.
Tracking who created comments or tracked revisions is one way to approach this but it would only get a percentage of those who actually edited the document and rely on those tracked changes and comments still being in the document.
If you go to File>Info you can see Word stores author(s) and last modified by names. So that should be available somewhere. If people were good enough to add themselves as authors in that view you might be getting a reasonable list. But of course it isn't going to be that easy - in practice the author is the person who first saved (or saved as) the file.
You could try investigating this code further - Built In Document Properties seems the best place for author and last edits.
Code:
Sub DocInspect()
Dim aDI As DocumentInspector, aDP As DocumentProperty
For Each aDI In ActiveDocument.DocumentInspectors
Debug.Print aDI.Name
Next aDI
On Error Resume Next
For Each aDP In ActiveDocument.BuiltInDocumentProperties
Debug.Print aDP.Name, aDP.Value
Next aDP
End Sub
To comprehensively explore the entire contents of a document to see if the info you want is there, unzip the contents of a docx file that you KNOW multiple people have edited and do a search across all the xml files to see if you can find some of their names somewhere. Don't search for the names that appear as author or last editor as you already know how to get those ones.