An insanely ugly way to do it would be to look for ^L in the original document and figure out where in the text they occur (non docx Word documents are mostly plain text: I sometimes use the strings command to read the content).
^L is control-L, character code 12 and sometimes called a "form feed". If you look at a raw Word document in emacs (or any editor that shows control codes), you'll see one of these at the end of each page.