Emeraldine base films were treated with HClO4 solutions of various concentrations, with and without the addition of NaClO4. The protonation of the films was studied using angle-resolved x-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) absorption spectroscopy, and ultraviolet (UV)-visible absorption spectroscopy. The protonation level can be substantially increased by the presence of salt if sufficient time is allowed for the anions to migrate into the bulk of the film. Conversely, in the partial deprotonation of emeraldine salt films, a higher retention of anions is observed in the presence of salt, even though the effect is not as pronounced as in the protonation process.