Proofreading is the final stage of checking for errors in a piece of writing before it reaches publication.
A proofreader's job is to find any remaining mistakes in spelling, punctuation and grammar in a document after it has been edited, and to resolve problems and inconsistencies in design and layout.
Typically, mistakes will be identified on the text using proofreading symbols (I am trained to use BSI symbols) or onscreen tools such as Track Changes in Word.
A proofreader's checklist will include headings, page numbers, references, footnotes, captions and labelling of diagrams and illustrations, as well as errors in the text itself.
Getting these elements right means that the final document will look more professional, communicate more effectively, and be much more enjoyable to read.