An important point about user-defined fields is that when you add a new field to the Marketing Documents object, the new field will appear in all document instances, for each document type.
The new field is applied retroactively to existing documents saved in the database, even if the document is closed.
When using the Copy To/ Copy From function to generate a new document from a base document, the value of a user-defined field is transferred to the target document. This also applies to documents generated through the Document Generation Wizard. If multiple base documents are copied, and the user-defined field has different values in these base documents, the field value is not copied.