Google Drive can be used to store just about any kind of file that you have. What a lot of people overlook is that you can use Google Drive to comment on those files without converting them into Google Docs or other Google Workspace formats. For example, you can upload a PDF to your Google Drive account, share it with others, and write comments on it without having to convert into any other file format. 

In this new video I demonstrate how to use Google Drive to comment on PDFs, images, and videos

Applications for Education
One of the ways that I’ve used this Google Drive feature in the past is to help my history students read through primary source materials. I would take a scanned copy of source that was available as a PDF, upload it to Google Drive, and then share it with my students. My students could then use the commenting feature to ask me clarifying questions about the document and I could use the commenting feature to highlight parts of the document to which I wanted to draw their attention.