Is there a simple way to prove it?
One way would be to compare the RGB color of the forged text and signatures against the average brightness of the paper. The paper brightness should vary since it’s not completely flat, and also because the scanning process always introduces noise into the measurements. I’ll bet the forger was SO amateurish that he used the same brush color everywhere. If so, do not pass go, go directly to jail, because they’re busted.
I contend that this is not only a case of forgery, but of identity theft. They clearly used portions of a real cert as a template.