A family of Microsoft word processing software products for creating web, email, and print documents.
Download http://www.gmayor.com/Zips/Envelope.zip which contains templates for size 10 envelopes, and change the paper size of the "Envelope - Air Mail #10.dot" template to that for the 6.75" envelope (you may need to use the Custom setting). Replace the graphics with your own.
To position the delivery address, click on it and then right-click the hashed box border that appears. Choose Format Frame. In the dialog that appears, change the vertical position (and the horizontal position if necessary).
Save the results with a different file name, in the Templates folder.