To run PDFreactor on a system without a graphical environment you should enable headless mode in java. To do so, you should pass the argument "-Djava.awt.headless=true" to the JRE which will run PDFreactor. Example:

java -Djava.awt.headless=true -cp ..\..\lib\pdfreactor.jar;. SimpleSample ..\din\pagestyles\header-footer.html header-footer.pdf