The “Letter background” Action allows you to add letter templates to existing documents.
These can be added on top of or below the document.

You can also provide a first and second page in the letter template. The first page of the template will then be placed only on the first page of the PDF being processed, while the second template page will be used for all subsequent pages.

Using “Manage letter head templates” in the menu at the bottom left of the Switchboard Action, you can add your own templates.

To load newly added templates, you must first click Back to leave the Action, then open the Action again.