A sales letter gives that reason and backs it up with examples and information. A sales letter is an important tool for shaping the way customers think of you.1. Successful case studies. Have you ever tried (or been tasked with) writing a sales letter? This article guides on creating compelling sales proposals, detailing key elements like executive summaries, product benefits, and company information. Sales letters can be physical or digital (such as above) and often range up to 10,000 words long. Request a release to use the information in the sales letter or other promotional pieces. Discover Pinterest's best ideas and inspiration for Sales letter example. Get inspired and try out new things. It's very quick and easy to create a simple sales introduction letter like the example above.