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.
Your reviewer sees the current image or PDF proof link and revision on the task before deciding.
Your approval task shows whether the reviewer can open the current proof before the due date, with a request for a corrected link when needed.
Keep reviewers aware of changes to a proof before they act on a decision. Your task shows the mismatch and asks for confirmation.
Your review tasks show the current image revision and reviewer due date, so the next handoff is clear.