What's the 'free CAD program'? Is it Google's SketchUp? If so (and it's a very good choice), learn how to use it...
SketchUp allows you to 'dimension' the drawing; to show the distance between two points, e.g. the ends of a line. In the menu bar, the dimension tool has an example dimension image (with a figure '3'). Just hover the mouse over each tool icon until the little pop-up "what's this" box says 'Dimension'.
Then simply select the line you want to measure (mouse click), and drag the mouse away from the line. This will drag the dimension away from the line, so you can see it clearly.
Alternatively, you can use the right-click 'Entity Info' dialogue to find line lengths, and areas of shapes.
You can use the Protractor tool to measure angles.