Firefox: If you'd like to print a website but the site isn't formatted well for printing, has ads you'd like to remove or other formatting issues, Print Edit enables heavy editing in Firefox Print Preview mode.
After installation, visit a site you want to edit before printing, click Print Preview in the Firefox File menu, and then from within the print preview, click the "Edit" button in the toolbar. Once in editing mode, you can select and deselect elements, hide and delete elements and do heavy tweaking in the Options Menu. The Options Menu contains such tweaks as altering the appearance of the print preview and changing the functionality of the "Format" button (what size the margins should be, the alignment, the list style and so on).
Print Edit is a free extension and works wherever Firefox does.