While printers are not all the same. Here are some helpful hints on how to print on both sides of a paper for Printable Cards.
Print out the first side of the greeting card using a color printer. Reload the printer after the first side prints out. In top loading printers, after printing the first side, turn the paper around, put the paper back inside the feeder to print the second side.
In bottom loading printers, put the paper back into the feeder without rotating it, in order to print the second side. Fold the paper into half so the cover and back of the cards show on the outside.
And to find printable cards click here.