Ten cards per sheet is true if you are dealing with pre-perfed card stock,
but if the OP is using regular card stock that isn't pre-perfed a yield of
12 per sheet is possible if landscape mode is used. Additionally, if all the
cards are identical, then setting the page size to 3.5 x 2 and then printing
multiple pages per sheet with top and left side margin of .25 will yield 12
cards in landscape. To make cut lines for these, I put a 1/4 pt. line in
each corner and have the line be as short as possible. When printed this
results in a cross pattern that isn't likely to show when cut, but is very
easy to follow.