The first place to look to uninstall Autodesk Plotter Manager is in the Control panel under the Uninstall a program area. Locate the program in the list, click it and choose Remove.
If it's not in that list, then it was probably installed with an Autodesk product as a support application, which means that you have to uninstall the full application to remove the Autodesk Plotter Manager as well.
Additionally, try using Revo Uninstaller. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.