Proofing is the final phase of the production of written work. It is a rigorous reading of text which has already undergone an editing process. Editing will have been carried out either by the author, or by an arm’s-length editor. A proofreader has expectation of correcting spelling, omitted or defective punctuation, and minor typographical errors which often hide unnoticed in dense text. While it is not strictly necessary for a proofreader to suffer from Obsessive-Compulsive Disorder, a streak of it is not a bad character trait to bring to the party.
Proofreading is not the correction of style, meaning, content accuracy, or structure. If a proofreader is bringing these matters to a writer’s attention, then the editing process has not been completed correctly and a good proofreader will stop what they are doing and send the whole work back to the author to undertake a better editing process.
In formal writing at tertiary education level, strict rules apply to the level of assistance a writer may receive when, for example, writing an essay or preparing a thesis. These rules are often published as part of a guidebook under the aegis of the of the University or Polytechnic at which a student is enrolled, or perhaps by another overarching committee such as the New Zealand Vice Chancellors’ Committee. Comparing these with similar publications from Australian universities, they all seem to reach the same conclusion: external proofreading of academic work is allowed, external final editing is not.
In other words, small mistakes can be eliminated without penalty and probably at any stage, but obtaining the services of an editor to deal with matters of content, structure and possibly even expression is strictly limited to the early stages of writing and should in all cases be acknowledged.