Question: What is Duplex Printing?
Answer: Most home printer users accept the fact that they can only print on one side of a page. If they need to print on either side of a sheet of paper, they re-insert the pages into the printer (carefully, making sure that the sheets are facing the right way and the right direction) and then print the second side.
This is fine for limited uses -- for example, if you're making some greeting cards, or doing a limited amount two-sided printing. But if you do a lot of printing on both sides of your paper, and you're getting tired of fussing with piles of printed paper, then you may want to consider a printer that does it for you.
Printing on both sides of a sheet of paper is known as double-sided, or duplex, printing. (Printing on one side is single-sided, or simplex.) Printers capable of double-sided printing usually have an internal tray that catches the paper after the first side is printed, flips it, and runs it through the print cycle again. This mechanism can also be called a Reversing Automatic Document Feeder (RADF).
A few printers have RADFs that are external, and can be added after you buy the printer, but for the most part, you need to opt for the duplex feather at the time of purchase. (You may see printer specs that say it has "manual" duplex printing -- all that means is that you get to reverse the paper yourself, but that the software will track what to print on each side of the page.)
Printers with RADF used to add a great deal to the cost of a printer. However, in the past year, duplex printing has become available even with mid-ranged all-in-one printers.
