Can you sue someone for slander if they call you a pedophile when that is what you are not?

Yes, but not necessarily.

This is a necessary condition, but an insufficient one. Three things must transpire for slander to legally occur within most jurisdictions.

1) A spurious and unsupported allegation must be made about a person. (Being called a pedophile certainly fits in this category.)

2) Other people aside from the slanderer and the slandered must hear this allegation. (I.e. If the slanderer and slandered are talking privately and no one can hear, no slander occurred. If the slanderer and slandered are talking in the middle of a shop around numerous customers and the same thing is said in a strongly disapproving tone, there may be slander pursuant to the third condition.)

3) Definable harm comes to the slandered individual on account of others hearing the slander. (Most commonly this is economic - i.e. termination, reduction in hours, reduction in business (if a storekeeper), or social - i.e. friend begin to abandon the slandered individual en masse. The social issues are harder to prove in a court of law.)

There is a second part of your question that many would not pick up on. "Can you sue" is both a question of permissibility (which was outlined above) and viability. Just because all three of the above criteria are checked does not mean that the civil lawsuit will be successful or that any firm will take the slandered's claim. If there are insufficient witnesses, the damages are too hard to prove, etc. a firm may not believe the case can bring enough windfall to pursue the claim.

Note: This answer is not attorney-client privileged, does not entail you to legal representation of any kind, and should not be construed as any viable legal text in any jurisdiction. (Necessary Boilerplate...oh well.)