cairo:ps-surface-set-size (surface width height)

surface -- a PostScript cairo:surface-t instance
width -- a number coerced to a double float for the surface width, in points (1 point == 1/72 inch
height -- a number coerced to a double float for the surface height, in points

Changes the size of a PostScript surface for the current and subsequent pages.

This function should only be called before any drawing operations have been performed on the current page. The simplest way to do this is to call this function immediately after creating the surface or immediately after completing a page with either the cairo:show-page or cairo:copy-page function.