You have dug up an old thread, and it is unknown if the original poster figured it out or not. When you get to a page that has a coupon you desire, just select Export to PDF from the Safari's file menu. If not using Safari, go to Print menu and select Print. There is in the bottom left of the print dialog box that allows you to save your page to PDF or Open Preview. Once opened in Preview, you can print from there if you agree with its appearance.
If neither works, tell us the page you are printing the coupon from. It is possible the coupon is designed only to work with a specific browser or a specific plugin. See my FAQ* on printers and FAQ* on browsers to see if it may make them more legible:
http://www.macmaps.com/browser.html
http://www.macmaps.com/printersx.html
* Links to my pages may give me compensation.