This article from BBC News gives some evidence for the return on investment of good document practices -- editing and proofreading.
It's not just documents destined for hard-copy printing that need proofreading. Remember to proofread copy for your website or blog. This often-overlooked part of the publishing process for online documents can have a big impact.
According to Charles Duncombe and the Confederation of British Industry, a single spelling mistake can cut your online sales in half.

