Save your letterhead as an image - .jpg for example - crop just the part you want as the letterhead at the top of your blank pages, save it again as .jpg, then insert it into a blank document and save that as your blank letterhead template. The image will be there (of the letterhead) and the rest of the document will be blank for you to write on as you wish. Just be sure that if you save any documents after writing on the blank template - you save them with their own name and leave the blank letterhead template blank.

Lisa