First I apologize for my English, I use an online translator to read and write and often confuse your texts.
I to fold the paper (short and long lengths) I do is mark the area of the crease with a fine-tipped pen (before using it I've got the ink and I have cleared the ball well to rotate properly)
Better than words I put some photos that make long
First I markings printed by the paper, but outside the drawing
After I turn the paper and makes a non-printed by the paper
I hope not to bother anyone with my comments.
Manolo