Google Drive is Google's file sync app that lets you store all of your files online alongside your Google Docs documents, and keep them synced with all of your devices.
Track which client proof requests the latest file addresses.
See which requested edits made it into a revised proof and which still need work, right beside the files on your review item.
Keep proof decisions visible through client delivery handoffs.
Your proof tasks show who decided, which file version they reviewed, and who takes the next step.