The idea is to have a toggle where you can have a faint line showing where a physical page would end (or where the print border starts) Example: I want to be able to write on a letter-size paper...
A great idea, however at this point this isn't a feature of either OneNote for Windows, OneNote Online or OneNote for Desktop. Only setting the whole page as a Letter or using Templates. It isn't like Excel where it defines the page by showing you gridlines with Page Break View etc. Maybe something to suggest back to the Team through the Feedback Portal? OneNote ยท Community (microsoft.com)