- In Word for Windows, choose File>Options>General and uncheck Enable modern comments.
- Then, on the Home tab, open the Styles Pane (Alt + Ctrl + Shift + s).
- Click on the Options button and set the Select styles to show dropdown to All styles. OK out.
- Back in the Style Pane, find the Comment Text style. Hover your mouse over the right end of the style name, then click on the down-pointing arrowhead that appears and choose Modify. The Modify Style dialog appears.
- Check the New Documents based on this template option, to make sure that future documents include numbered comments.
- Click on Format>Numbering and choose a numbering style for your comments. OK out.
In testing here, this adds numbers to each new comment, but does not add numbers to old comments.