How to modify Print Format when the document is in Print view

I need to know if it is possible to configure the print format when the document is in print view (the view after press Print buttton).
I have a image for the print format that need to be expanded near the border of the page, but I do not know what CSS properties have to change to do this.

The print format is rendered on the server, so you just need to call it again. If you have a two print formats for your doctype, switching back and forth is the easiest way I’ve found. Otherwise refresh the screen.


I think I did not explained it very well. I am referring to the format/features that the document has when it is in the print view, after pressing the Print button and before printing the document. That is what I refer:

I want to act on this format, expanding an image that I will use as a background to the edge of the page.

Ah! That is a PDF being shown in your browser so you want to edit the print format before you get to a PDF.
What timezone are you in? This could be solved with a very quick screen share.

Yes! it is exactly what I want.
My timezone is Europe/Madrid (CET, +0100). What would you want a screenshot of?