How do I create a PDF invoice with no margins in Numbers '09?

Hi,

I am looking for a way of creating an invoice in Numbers '09 with absolutely no margins, for exporting to PDF. Even if I remove all margins and header and footers on a page, Numbers still leaves behind a margin at the top and the bottom. This means that if I want to create an invoice with a background image to fill the entire page, I can't do so.

Ideally then I would be able to remove these 'margins'. Failing this, is there a way of setting the background colour for a page using Numbers? I have tried doing so through "Show Fonts" but nothing happens when I try to change the colour.

I'd be grateful for any advice in getting this working.

Thanks,

Nick