I wish Pedro would shoot as much as Ronaldo
I don't.

The major reason his conversion is so good is that he is very picky about what shots he takes. He is a La Masia player- if there isn't a high probability of conversion, his instinct is to move the ball to a player with a better position, or to safety. Though sometimes we wish Barça players would take slightly more risky shots, or not make that extra pass (see the ultimate inexplicable pass below), on the whole this tactic pays off.
Pedro taking more shots does not necessarily mean he'd score more goals. More likely, his conversion rate would simply plummet. Think of it more as Pedro, seeing the same opportunities as Ronaldo, is smart enough not to shoot the same shots Ronaldo would miss, giving Barça a look at goal somewhere else on the pitch rather than turn the ball over or leave it to chance.