Unfold the pastry sheet on a clean work surface. Sprinkle with 2 tablespoons of the cinnamon sugar. Starting at each long side, fold the pastry toward the center, leaving a 1/4-inch space in the middle. Sprinkle with the remaining 1 tablespoon cinnamon sugar. Fold one side over the other, making a 4-layer rectangle. Cut the rectangle into twelve 3/4-inch slices and put the slices cut-side down on baking sheets, about 2 inches apart.
Bake until golden brown, 15 to 18 minutes. Use a spatula to transfer them from the baking sheets to cool on wire racks.