A collection of DocumentProperty objects. Each DocumentProperty object represents a built-in or custom property of a container document.
Remarks
Use the Add method to create a new custom property and add it to the DocumentProperties collection. You cannot use the Add method to create a built-in document property.
Use BuiltinDocumentProperties(index), where index is the index number of the built-in document property, to return a single DocumentProperty object that represents a specific built-in document property.
Use CustomDocumentProperties(index), where index is the number of the custom document property, to return a DocumentProperty object that represents a specific custom document property.