This dissertation investigates social annotation use in undergraduate reading and writing courses. It comprises three interrelated studies that examine different aspects of social annotation practices and pedagogical decision-making. The first study focuses on student annotations and analyzes students' knowledge construction practices. The second study shifts the focus to instructors' decision-making processes as they design and use social annotation in their courses, by identifying instructors' practical wisdom and pedagogical reasoning. Finally, the third study examines social annotation as part of a larger activity system and explores how it mediates other course activities and goals. The first study reveals that interpretation and elaboration are the most common knowledge construction practices students use in their annotations. However, variations are observed between instructors and between initial annotations and responses, highlighting that instructional design and pedagogical approaches impact students' use of social annotation. The second study identifies two themes of instructors' decisions regarding their implementation of social annotation: annotation as preparation and annotation as participation. The study identifies the practical wisdom instructors demonstrated as they navigated those decisions, providing a valuable resource for other instructors looking to implement social annotation in their own courses. The third study illustrated the interacting elements within the social annotation activity system. Additionally, instructors identified multiple purposes for social annotation activities. This sometimes created tensions within and between the activity systems because certain purposes did not align well with overarching pedagogical goals. This study provides models of activity that can be useful for instructors in visualizing the complexity and tensions when implementing social annotation and aligning their implementation with other activities and pedagogical goals. Together, these studies offer a comprehensive and nuanced understanding of instructors' social annotation practices in undergraduate writing and reading courses. They highlight the importance of considering various contextual factors in promoting effective use of social annotation, including instructional design, pedagogical approaches, and alignment with other course activities and goals. The findings and implications of these studies can serve as a valuable resource for instructors looking to implement social annotation in their own courses and for researchers interested in the use of social annotation in higher education. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]