By default when a document is attached to a patient through Document Management, an automated message will be generated to the receivers as set up 

in Admin -> Messaging for Documents Uploaded

However, for certain Document Types you can turn this off so the checkbox to "Not Send Automated Message" is checked by default. This is done through Admin -> Lists -> List Item Entry, select the Document Types list on the left and then for each one you do not want a message generated for, select 

Non-Medical under the column for Medical Indicator.