Secure file upload and client login

I need a plugin that will allow me to create and send clients a username and password to login through my site and upload small pdf/doc files. I need to be able to leave comments beside their file uploads on my server to say that the files have been assessed or if I need additional files. They can then login at anytime to check the progress of their assessment. Is there a plugin that will do this or something close that can be customised?

Thanks