There have been a lot of issues with the pumps and pulleys over the years. The original pulley on and original pump shaft was a slight press fit. Unfortunately, most of the repro pumps and pulleys are more of a slip fit. Even worse, most of the pulleys and pumps from different suppliers have fit issues. So...
Chances are a puller will not be necessary. If it is, it would be easiest to remove the pump to work on the assembly. In fact, that is how the manual tells you to do it...install the pulley on the bench. It is possible to remove the pulley on the engine, though, if he insists on doing it that way. Remember that one of the water pump bolts must be inserted before installing the pulley!
I recommend buying the pulley with a new pump, and both from the same supplier. Then, use the proper washers and/or spacers, so the pulley becomes locked tightly between the shaft step and nut washer. Any play causes the pulley to eventually wallow on the shaft, and like Charley pointed out, that destroys both the shaft and pulley.
And, just a thought...the most common cause of a knocking at the front of the engine is a broken camshaft chain tensioner (also a repro problem). Second is usually a loose dynamo.