Use Box Web Documents:
These are authoritative documents that live on the Box service and cannot be downloaded and edited outside of the Box environment. When a team member views a Web Document it is automatically locked to ensure the document does not get edited in parallel, preventing the creation of multiple, slightly differing copies of a document that must subsequently be compared and merged into an authoritative document. Collaborators will know when a document is being viewed by another team member because it will be grayed out.
Enter notes in the document Comment section:
Existing documents in formats such as Word, Excel, and PowerPoint can have a running set of comments that can then be consolidated into an authoritative document managed by a designated individual.
To add a comment, click on the icon to the right of the document's name. A comment window will appear below the document name. Click "Add Comment" when finished to add the comment to the document.
Documents with comments will display a number over the comments icon indicating the number of comments attached to the document.
Recovering from accidental overwrites
Files accidentally deleted or overwritten are retained on the service for 30 days so they can be easily recovered.