Folder permissions

We have our documents folder at the project level visible by all since many of our requestors/clients need to upload content (images, text docs, reference materials). But we are finding that some requestors are going through our design folders and finding proofs that are not ready for client's eyes! When they open in proofing, they are automatically added to the workflow and can now see all the comments that are only meant for our internal team. Is there any way to lock this folder or document so they cannot see the proof before its ready for their review? Or do we need to remove their permissions to the documents folder and have them send their content in a different manner? The later is not ideal since our process was going relatively smooth except for one or two anxious clients. Jennifer Cournoyer Senior Communication Designer/Manager Brown University, Advancement Providence, RI