Does pitcher pitch calling (PC) make a difference ... say in shaking off the catcher's pitch call ... for example does a pitcher with a PC of zero change the catcher's pitch called more than a pitcher with a PC of 34? Or is it simply a number that is never really used for a pitcher? or Given equal abilities will a pitcher with a PC of 34 produce a lower ERA than a pitcher with a PC of 0?

No, it's not used for pitchers.

I never did pay any attention to it but after playing 36 seasons I just thought I would ask.

PC rating is a catcher rating. It is not a pitcher rating. It only effects the player inserted to play catcher. It rates how effective a player is at calling pitches from the catcher position only. Example: All players are rated for control and velocity, however it is only used if the player is pitching. The same is true for PC, it is only used if the player is catching.  

The reason I had thought about it recently is that I seemed to notice more pitchers shaking off catchers calls in the MLB and thus wondered if that was built in to HBD ... I have 3 pitchers on my current HBD team with a PC of ZERO  so I have not paid attention to it ... I was just wondering if shaking off catchers might have been built in based on watching current MLB games

If my pitchers have a PC of zero, there is no way I would start them behind the plate!