First principle calculations are presented of angular distributions of electrons ejected from the CO-covered Pd(110) surface using metastable He* beams as soft probes (i.e., surface Penning ionization). Excellent agreement has been obtained in comparison with recent available experimental data. These theoretical results indicate for the first time the importance of intermolecular and intramolecular shadow effects and surface corrugations and show that CO stands perpendicularly to the surface with oxygen towards the vacuum. The great surface sensitivity of angle-resolved surface Penning ionization (ARSPI) to adlayer electronic and geometrical structures has opened a new area for surface applications.