I tried this macro. I pasted it in exactly as provided except, because my footnote numbers aren't bracketed or enclosed by anything else, I changed:
.Text = "\[([0-9]{1,})\]"
to:
.Text = "([0-9]{1,})"

I also selected a group of footnotes at the bottom of a page. When I ran the macro, I got the same error message:
Run-time error '13': Type mismatch

I then clicked "debug" and it highlighted the following line in yellow: k = .Paragraphs(1).Range.Words(1) - 1

Did I do something wrong? Any advice what to try next?