You can leave comments on a document using Google Docs, which is a great tool to support student learning, since you can highlight specific parts of a document and directly comment on those parts if you wish. Using Google Docs, teachers are also able to keep track of how students are modifying the document, which makes it easier for them to monitor how they are observing the document.  This helps teachers identify any mistakes or issues that the student may have with their work, and allows them to provide helpful guidance. It also encourages students to take ownership of their work, as the teacher can clearly see and evaluate all of their changes.