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 review task shows file access problems before review starts. The owner sees what to fix.
Your creator gets the reviewer's requested changes and current draft together, so they can start the next revision without chasing files.
Your campaign team gets a shortcut to the approved asset in its launch folder, with no handoff to chase.