In a study of notetaking in university courses, we found that the large majority of students prefer paper to computer-based media like Tablet PCs for taking notes and making annotations. Based on this finding, we developed CoScribe, a concept and system which supports students in making collaborative handwritten annotations on printed lecture slides. It includes mechanisms for the paper-based sharing and semantic tagging of annotations and slides. Moreover, we present a novel visualization of shared handwritten annotations providing an integrated access to annotations from all learners. The results of a user study indicate that CoScribe efficiently supports student annotation and can be easily integrated into current annotation practice. (Contains 10 figures.)