Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain and transfer pasta to slow cooker.
Add butter to pasta and stir until melted; season with salt and pepper. Sprinkle about 1/2 the Cheddar cheese over pasta and stir.
Whisk evaporated milk and eggs together in a bowl until smooth; stir into pasta mixture.
Whisk milk and Cheddar cheese soup together in a bowl until smooth; stir into pasta mixture. Sprinkle remaining cheese over pasta mixture; garnish with paprika.