A Proofreader bears an important role in any project to do with written content, like social media copy, novels, essays, or even films. This role may differ from one job to another, as different content needs different treatment. Still, it generally requires a person to examine the document for any signs of grammatical or formatting errors.
More often, though, the Proofreader will be asked to make sure that the document's style is consistent and to see whether it lines up with the company's style guide. They may also be asked to check the work of other proofreaders. In terms of creative works, the Proofreader may even act a bit like an editor, noting what could and should be changed to make the work easier and more enjoyable to read.
A good grasp of the English language and an eye for details are important for this position, though there is no one set of requirements that a candidate must have. Some employers may ask for a college degree, while others will not. Either way, to begin one's career as a Proofreader, there's really no right way.