Proof reading is that craft or technology or skill that reduces the number of errors in a written document.

It deals with spelling, typography and grammar but not with the point of view that the author is explaining. A proof reader does not have knowledge of the author's craft.

We only deal with large-ish, mostly technical, documents especially those which have been written by authors whose first language is not English.

We use software to identify the most obvious errors and this enables us to very much shorten the processing time.

Contrary to popular belief, proof reading is not just a matter of correcting perceived errors. Sometimes, especially in the English language, non-grammatical artifice is deliberately introduced for effect.

While the proof reading process ought to show such matters to the author, the proof reader has always to bow to the author's intention.