Users have asked for the ability to email or print documents with callouts. Since callouts are floating layers they are not included when you email or print a document. Also, Key Docs are always editable, i.e. you can always move or delete a callout, or clear the annotations (including a redaction). The Snapshot makes a flattened image of what is displayed and it can't be altered. This can also useful if you want to import a PDF of a Snapshot with a callout into another application like Word or PowerPoint.