I can't find anything that shows how to hide the document and only show footnotes.
view tab/Draft view/references tab/show notes will show them, but it should leave document showing.
In this article, we will show you 3 effectual ways to view all the footnotes at once in your Word document.
www.datanumen.com
I assume its not a memory problem and the documents is so big it can't show it on screen, that seems unlikely