Cognitive and cultural embeddedness: combining institutional economics and economic sociology
According to this, pederasty is sexual relations between two males, especially when one of them is a minor. Other definitions, like the one that JSBangs found, differ slightly. But otherwise, I think you answered the question yourself: pedophile refers to the attraction, while pederasty refers to the act itself.
Which brings me to the crux of it. My understanding of these words is that. A pedophile is sexually attracted to children. A pederast has sex with children. Therefore, one can be a pedophile without having sex with children, and as a matter of fact, once a pedophile has sex with a child, then that person is a pederast. pederast has sex with children. Therefore, one can be a pedophile without having sex with children, and as a matter of fact, once a pedophile has sex with a child, then that person is a pederast.