Sketchup is a free CAD software which works great for creating templates for leather projects. Even though this is a 3D software, it works well for 2D patterns as well.
1) Setting up
Open Sketchup, and create a new project. When selecting a project template, choose the woodworking template, in either mm or inches.
Switch the camera view to "Top"
Enable the measurements toolbar
2) Draw your guidelines
Guidelines are essential, because your drawing tools will snap to them in order to place your objects precisely.
Select the tape measure tool
Using the measuring tape, you can mark distances from one point to another. In this example, the y-axis was selected and a distance is marked to the right of the y-axis.
After selecting the first point, move your cursor in the general direction of the guideline you are hoping to make, and then type the exact distance and press enter.
3) Draw your pattern
Using the drawing tools, draw your pattern.
I suggest installing the bezier tool plugin, in order to draw more complicated curves than the built in tools allow:
Example drawing with lines and a bezier curve:
4) Print your template
Change your camera to a Two Point perspective.
Be sure to deselect the "Fit to page" option in the print settings. This option resizes the model to fit the paper, which we do not want. We want to print actual size.