Information literacy has become one of the most essential skills we teach undergraduates. One highly effective way of teaching this skill is to put students in the active role of the mediator by asking them to produce a critical edition of an existing, open-access text. The process of inserting explanatory footnotes, writing introductory material, or creating an appendix of cultural contexts teaches research skills for interacting with a wide range of primary and secondary texts. Furthermore, critical editing foregrounds questions of audience and purpose that are essential to metaliteracy. This article discusses a footnoting assignment I designed for an undergraduate humanities course in which we read Edward Jenner's 1798 pamphlet on vaccination against smallpox, An Inquiry into the Causes and Effects of the Variolae Vaccinae. I developed a sequence of three research assignments that asked students to use online annotation software to create an edited version of Jenner's text aimed at their fellow students. In the first assignment they worked in groups to define key terms, identify the main points of Jenner's argument, and pose critical questions about the text. In the next two assignments, students conducted independent research in nineteenth-century periodicals to discover the popular debates surrounding smallpox and Jenner's work and then used their research to insert explanatory footnotes into Jenner's text.