When using a networked printer, that ‘page preview’ thing never works well enough to be relied upon. Inevitably the printer is located half a day’s walk away from your desk, so you will make a print, trek, gasp in surprise at the ugly errors it contains, bin it and repeat a few times.
This wastes time and paper.
Today’s invention is a network printer which scans what it has just printed and sends you a copy electronically. You will almost certainly want to improve on the first version, so it will then offer you the option of feeding the paper back through the machine for another print on the other side.