The choice of paper type is also presented by using a menu that contains a bunch of different options.
An important element to consider when working with Quite Imposing is that the amount of changes made to a PDF document are stored until the next time it is opened. This means that the adjustments are saved even after the document is closed, and when it is reopened it uses those changes to construct a new page.
There is no such thing as a free lunch though, in this case, the plugin 6add127376