Chrome: It's not that difficult to download email attachments and add your notes to them, but wouldn't it be nice to review the attachment, add your feedback in-line, and send it back right inside of Gmail without even downloading the file first? Framebench can do that.
One of the nice things about Framebench's annotation extension is that the other party doesn't even need to have it for it to work. With the extension installed, you can open any attached file or image in the native viewer, add your notes to it, then save it and send it back to the original sender.
The updated file is also attached to the message directly, so the other party doesn't have to sign up for an account or jump through hoops in order to retrieve it or see your notes -- they're all clearly laid out in your message. Hit the link below to learn more, or to give it a whirl.