Yes Paul Reubens swears in
Cheech and Chong's Next Movie
but his character is a hotel desk clerk, not Pee-Wee Herman. Pee-Wee Herman is just a character that the desk clerk plays while he is on stage doing an act. Notice how the desk clerk isn't dressed as Pee-Wee nor does he act like Pee-Wee. He only dresses and acts like Pee-Wee when he goes on stage and does his comedy. So, yes he swears, but he isn't Pee-Wee Herman when he does.