It uses the standard called PWG 5101.1-2002 PWG: Standard for Media Standardized
Names to name the paper sizes (and to get the data for the page sizes). In addition to standard paper sizes, GtkPaperSize allows to
construct custom paper sizes with arbitrary dimensions.
The PaperSize object stores not only the dimensions (width and height) of a paper size and its name, it also
provides default print margins.