So you don't have such a program, is what you're saying?
Any vector application will do that for you easily - Adobe Illustrator, CorelDraw, Xara Designer, Inkscape and there are many others. However, the first three cost money (I use Xara Designer, myself.) So for a budget of $0, you should probably download Inkscape which is free Open Source software.
By keeping your goals simple, as in rectangles for trucks and other vehicles or buildings it should be fairly simple. All these vector apps can rotate in single degrees and in some cases 10th's of degrees. So you have lots a maneuverability to fill your needs.
That's my recommendation anyway.
GP