So like Jeremy, I fired up Google Docs. I uploaded the Important Doc there (hope nobody from Security is reading this, though the doc was intended for folks outside of my company.) It came through just fine. I made the edits I needed to make and saved it on Google Docs.
Then I went back to fixing Office, which I eventually did. I went in to work, opened the Google Docs version of my document, and manually merged in changes to the original. I would've just exported it as a Word Doc, but I was afraid of how it would handle the table of contents. So I manually merged and then updated the table of contents.