Just put the page number frame at the bottom of your master pages (or I do not understand the issue)
It is at the bottom of the page on the Master Page. The Master Page is 8.5X11 letter size. If I make a document page taller, say 11X11, then the page number is not all the way at the bottom.
Why don't you set up different master pages at different sizes with the page number at the bottom of each master? You don't know in advance the new size?
Create a separate Master page for each page size you are using. You can change the size of each Master Page (or Master Spread) as you set it up using the Page Tool. Then place a text frame at the bottom of each Master positioned from the bottom the same distance for all Masters. Each of these text frames should then have the automatic page numbering function active in it. To do this click inside a selected text frame with the text tool and then use Type Menu>Insert Special Characters>Markers>Current Page Number. Then when you apply your Masters to all of your document pages the page number will be in exactly the same spot relative to the bottom of each page.
Good idea. I'll try that.
That is exactly what I wrote…