This document describes a professor's use of collaborative online annotation to blend a reading assignment. The professor had students annotate PDF versions of assigned readings using an online tool before class. This allowed the professor to see students' questions and comments on specific passages before class. It also facilitated discussion by having students engage with each other's annotations. The document discusses the pedagogical goals of blending the assignment, criteria for selecting an annotation tool, an example of student annotations on a passage, usage data on student participation, and student feedback on the tool.