Fold the paper at the pencil mark, making sure the edges of the paper line up. Make a crisp crease along the whole length of the paper and then unfold the paper. Cut the paper (on the roll side) about 1/2-inch away from the fold.
Remember: All the paper edges of a wrapped gift should be folded under so that you don't see any cut edges, whether they've been cut by you or the papermaker.