Advance pages are pages that are to be prepared before their final edition exists. For example, you want to work on a page that is to be published in about three months ago. Its final edition is not yet created.
Use any page in a temporary edition for this purpose. When a final edition is ready, you will move the advance page from the temporary edition to the final edition.
Important
Dimensions & names of master pages in the temporary edition must be identical as the dimensions & names of master pages in the final edition.
Note
The page number and folio are not important at this point, as they will be inherited from an appropriate master when you move advance page in the final edition.