Adding File Path to footer in Pages

No. Possible by setting placeholder text in the footer (e.g. [path]) and then using AppleScript to get the document's file path and replace the placeholder text with that path string.

The other manual possibility is to switch to the Finder without leaving Pages and locate the Pages document you are working on. Press the option key and right-click on the document, selecting the Copy "foo.pages" as Pathname menu item. Then back in the Pages footer, just paste that path from the clipboard. If you do not want your user name appearing in that path, replace it with a tilde (e.g. ~/Desktop/foo.pages).

Neither of these possibilities will automatically change the path in the document if the file location changes.