Commenting in Google Drive Preview

There is no longer a need to open files with other applications to review and leave comments or assign tasks. For Microsoft Office files, PDFs, images, videos and other files you can now update and view comments in the Drive preview pane.

To add a comment to a file, use in the Drive preview pane. When you leave a comment on Microsoft Office files, the comments will still appear when you open the file in Microsoft Office.

Please visit the Google Drive Help (external link, opens in new window)  page for detailed instructions on how to leave comments on the various file types.