Kami is an online document annotation and markup tool. You can highlight, underline, and strikethrough text in PDF and other document formats. You can also add text boxes, shapes, and images. Kami works with Google Drive and Google Classroom. With Kami, you can easily collaborate on documents in the classroom while avoiding the hassles of printing documents.
Kami Educational Resources (blog) including tips and tricks, suggested curriculum (sketchnoting, assessments, collaboration)
TextHelp PDF Annotator (from R&W)
Click the link to view video tutorials on how to use TextHelp PDF Annotator