Either the right-to-left method or the two-column table method will work if you only want numbers to the right. If you want them mirrored for duplex printing you will need to use the method I describe.

Note that if you also have ordinary numbering on your paragraphs, i.e. at the beginning, as well as the marginal numbers, you probably would want to use the method I set forth (which does not have to be mirrored).

If you are using either of the other methods, you should review and use the methods for numbering set forth in How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly. That numbering is attached to styles.

When I think of it, I would guess that the method with frames could also use style-based numbering rather than the SEQ field.