

Proofs are then returned to the typesetter for correction. Unlike copy editing, the defining procedure of a proofreading service is to work directly with two sets of information at the same time.

Traditionally, a proofreader looks at an increment of text on the copy and then compares it to the corresponding typeset increment, and then marks any errors (sometimes called 'line edits') using standard proofreaders' marks. They may contain typographical errors ("printer's errors"), as a result of human error during typesetting.

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