it is supposed to just come off, but 15 - 20 years will change that a bit, sometimes.
the first time i did it i ''tapped'' threads into the 2 holes on the pulley and then used a puller i borrowed from autozone.
since then i have managed to get them off without going through all that. i usually , carefully tap on the center section of the pulley with a hammer to ''break'' the seal and it slides off. use some spray lube . careful not to damage the vanes on the outer edge of the pulley