On Tue, 8 Jan 2008, Matthias Drochner wrote:

> [paper size]
> joerg@britannica.bec.de said:
> > Why do you not set that in the document itself? 
> 
> How? The standard document class options set only
> margins internally for formatting. There is no effect
> on the media size directive seen by the printer or
> PDF viewer (MediaBox in PDF, setpagedevice in PS).

I use the geometry package. For example:

\usepackage{geometry}
\geometry{verbose,paperwidth=7.44in,paperheight=9.68in,tmargin=0.72in,bmargin=0.72in,nomarginpar,rmargin=0.60in,lmargin=0.72in}

for ISBN 978-0-9790342-2-0

Also some document classes take options for defining page size, like:

\documentclass[a4paper]{article}

The layout package could also be used.