Select the one you want to cross-reference to and then click Insert.
When you do that all of your numbered paragraphs will appear in the "For which numbered item" box at the bottom of the dialog box.
Image courtesy of Microsoft Step Right-click anywhere in the selection and choose Update Field or press the keyboard shortcut F9.
I've managed to sort out the paragraph spacing, tab stops, the works.
There are many instances in the document where there are paragraphs lower down which cross reference paragraph numbers earlier in the document. As per paragraph 12.3 above, the parties have agreed ... The result is that if you download the final docx generated file, and then delete paragraph 12 (for some reason) the lower down paragraphs WON'T update the cross-references for the other paragraphs.
Of course, you can manually change your footnote numbers when you’re done writing, but this can be tedious.