First off, your right, I don't have the map just the digital file, so the scale I took a screen shot of is off.
Second after much online research for freeware I can prove you right!
I found two tools.
The first is an online protractor that is a yahoo gadget, very elegant works well, opens up on top of anything on your desk top
The second is an online ruler program. Once you open it you can calibrate your units by measuring between two known points. Once you've done that , you can measure between any two points on the map
Process I followed was to measure one square and set it as 10,000 meters. Than I measured between Verdun and Metz and got a measurement of 57,340 meters, or 57km
Finally I layed the Protractor over the line and got a heading of 93 degrees.
Fantastic! This means I can take screen shots of mission maps in game with bases, targets, ballons, and create waypoint maps with accurate distances and headings.