Place the printed side face up, with the leading edge (top) of the paper in first. To print on the second side, place the paper face down with the leading edge (top) facing up. If using letterhead paper, insert it with the heading facing down and first. Then use a pencil to mark a diagonal line from corner to corner on each page. On one side only, fold along the lines until you reach the back side where you can unfold them. This method is easier than flipping it over manually and works well for printing multiple copies on both sides of the paper. If you don't want to use pencil or pen, then simply mark the diagonal line on one side only and turn the paper over when reaching the other side. This method is easy to remember and does not require any additional equipment. It may be helpful to refer to a print instruction sheet available from most companies that provide this service. These sheets usually have the opposite direction written in big letters at the top of the page to help you print single-sided and double-sided papers. They are also helpful to note which paper type requires what orientation when printing from computer files. Companies that provide this service often charge by the page or by the number of copies required. They may even have special rates for college students or those who work for them.