The term “proofreading” is bandied about in our industry when dealing with translations or simple publications of writings in one language that are not translated. Yet many of the people I have encountered have no real training in the craft, so it is important to establish exactly what a professional agency would be looking for from a proofreading.
There are two principal aspects to a proper proofreading: grammar and style. Of primary importance are the hard-and-fast grammar rules that need to be followed in every piece that is published by an agency, company, etc. Everything from typos to dangling participles need to be corrected so that the best possible image of the company is put forward at all times. “Style” is a more elusive beast because it is ambiguous and subjective. This aspect comes into play more often on longer pieces that were translated or composed by multiple authors and then brought together into one work. Obviously, the idea here would be that these disparate sections come together seamlessly and the tone, color, and flavor should remain consistent throughout the piece, with special attention being paid to any specific requests made by the client/publisher/author. These requirements necessitate that the proofreading be done by someone who is a native speaker of the target language who also has studied the art of writing and text cohesion in some capacity.
In short, proofreading a text is not a matter of making sure that all the right words are capitalized. Instead, it is looking at the document, whether it is 1 page or 1,000, as a whole and, in addition to correcting all errors, deciding if each and every word fits or if there are better options.