Pedophiles =/= Sex offenders. Pedophilia is a psychiatric disorder and pedos do not always act on it-- some realize there's something wrong with them and seek psychiatric help, but largely it's like sexual orientation that doesn't change.
Sex offenders are all those that act on it, although not all sex offenders are pedophiles, some are opportunistic.
The word pedophile is commonly applied indiscriminately to anyone who sexually abuses a child, but child sexual offenders are not pedophiles unless they have a strong sexual interest in prepubescent children.
Sources 21-23 are relevant. Check out the Wiki page on "Pedophilia" as well if you want to learn more. It's a tragic condition.