The interaction between charged surfaces bearing terminally attached polyelectrolyte chains is investigated using Monte Carlo computer simulations and a mean-field theory. In particular we focus on the role played by the addition of a simple electrolyte component. It is found that the force between the surfaces increases with increasing electrolyte concentration because of a repulsive osmotic pressure contribution due to the small ions, while the attractive bridging component is insensitive to added salt. Considering the approximate nature of the mean-field (polyelectrolyte Poisson-Boltzmann) theory it compares well with the computer simulations.