You can collaborate on Pages documents stored in Box. Just like when you’re collaborating on a document stored in iCloud, everyone can work in real time and see changes as they’re made. When documents are stored in Box, however, you need to use the Box controls to invite people to collaborate, set sharing options, or to stop sharing. (Box collaboration controls appear automatically after you click the Collaborate button in Pages.)
Before you can share a Pages document, you (or your organization) must enable iWork collaboration in Box Account Settings. If the document you want to share isn’t already stored in Box, move it to Box. You can place the document in a shared folder (to share it with everyone who has access to the folder), or use the collaboration controls to invite only specific people.
For instructions and system requirements, see the Apple Support article about iWork documents stored in Box.