A new feature of CrowdGrader enables reviewers to upload files with their review. In this way, students can collaborate with reviewers using any file format, from pdf, to doc, to file bundles for code. For example, students can download essays or papers in pdf/doc format, annotate them in place, then upload the annotated versions of the files together with their reviews.
This feature is already in successful use in some early-adopter classes. We hope it might be useful to you!