Firefox allows you to modify the top, bottom, left, and right margins for your print job. To do this, first click on the Margins & Header/Footer tab, located at the top of the Page Setup dialog. At this point, you will see a section labeled Margins(inches) containing entry fields for all four margin values.
The default value for each is 0.5 (half an inch). Each of these can be modified by simply changing the numbers in these fields. When modifying any margin value, you will notice that the page grid shown will resize accordingly.
