No Automatic Adjustment of Print Size. In IE, increasing the size of a Web page on the screen also increases the size of the page's text when you print it out great for those with failing vision. Firefox, however, prints every page at the same magnification, no matter how large you make the type on your screen. To adjust the text size on the printout, you'll need to use the File, Page Setup dialog box. Or you can click File, Print Preview, and use the Scale widget to adjust the printed text size in real time until you're happy.
I tried the above and it works. Go to print preview and adjust the scale widget like the man says