The document discusses the role and responsibilities of copy editors and proofreaders. It provides guidance on common errors to correct such as errors in fact, grammar, opinion in news, word usage, libelous content, and vulgar language. It also outlines copy editing symbols used to mark corrections, changes, subheadings and headlines. Instructions are given to copy editors on techniques like using a soft pencil, writing legibly, erasing marks to cancel corrections, and retyping copies with many changes. The roles of linotypists, typesetting machines and operators in introducing errors are also outlined. Proofreaders are tasked with catching errors from the copy reader or introduced during typesetting and printing.