Complex sentence: Sarandon has contributed the narration to some two dozen documentary films, many of which dealt with social and political issues; in addition, she has served as the presenter on many installments of the PBS documentary series, "Independent Lens".
Split into simpler sentences: Sarandon has contributed the narration to some two dozen documentary films, many of which dealt with social and political issues. In addition she has served as the presenter on many installments of the PBS documentary series, "Independent Lens".