Writing slopes or document holders can have a massive impact on posture and prove to be one of the most cost effective ways of combating back pain. One of the more common causes of back pain, aside from sitting in the wrong chair, is referring to paperwork directly on a desk top.
This forces the user to lean forwards over the desk, placing the body into an unnatural posture and placing strain on the whole body, particularly the lumbar, thoracic and cervical areas. It is better to have the paperwork higher on the desk, and at a more beneficial angle of view, to help keep the head naturally supported over the spine and the back more upright or reclined if possible.