The letterhead is inserted using the Merge Document command:
The insert document command as shown here is the equivalent of searching for the documents that have the text "generic" and "letterhead", as shown here:
Since only one document is found, it is automatically inserted in place of the code. The Generic Letterhead contains:
which when merged in results in the equivalent of
As you can tell, the idea of being able to insert a document into another one is very powerful, giving you the ability to define key portions, in this case the letterhead, and then reusing that in many other documents.
You also gain the advantage of only having to change your source documents, eg. the letterhead, once and have it apply consistently everyehere where it is needed.
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