A GtkPageSetup object stores the page size, orientation and margins. The idea is that you can get one of these from the page setup dialog and then pass it to the #GtkPrintOperation when printing. The benefit of splitting this out of the #GtkPrintSettings is that these affect the actual layout of the page, and thus need to be set long before user prints.
Fluent builder for gtk.page_setup.PageSetup
Fluent builder implementation template for gtk.page_setup.PageSetup
Module for PageSetup class