We obtain a general expression for the optical transfer matrix of spatially dispersive conducting films surrounded by a local material in terms of their odd and even surface impedance. This matrix simplifies the calculation of the optical properties of multilayered conducting heterostructures. As an application we calculate, within the semiclassical infinite-barrier model, the absorptance of a semi-infinite conductor-insulator superlattice, taking into account the excitation of plasma waves and electron-hole pairs at the conductor's boundaries within the semiclassical infinite-barrier model. The results are interpreted in terms of the normal modes of the system which include coupled surface plasmons, guided bulk plasmons, and transverse waves. The presence of electron-hole pairs increases the absorptance and cause a sizable shift and damping of the guided plasmon resonances.