Like the definition of “football” and the use of the metric system, Americans also differ from most of the world on the definition of a standard paper size. Most of the world uses a standard paper size called A4 for letters, which is why SAP has chosen that paper size as its default for SAP BusinessObjects Web Intelligence. But in the United States (and also Canada), a different standard exists for letter-sized paper.
Changing the default page size, default margins, and default header and footer size for Web Intelligence can all be accomplished by modifying the WebIDefaultStyleSheet.css on the SAP BusinessObjects BI server. My article on the EV Technologies web site, Web Intelligence Default Paper Size, has all of the details.