What is proofreading?
If the copy-edit is your first line of defence, the proofread is your last. Your proofreader is there to make sure those potentially embarrassing mistakes don’t make it through. They will also check that the text is consistent with your editorial style guide (see copy-edit).
If your project contains images, captions and cross-references, these will also be checked by your proofreader, along with running heads, page numbers (known in the publishing industry as folios) and any other design elements, to see that they make sense and are in print-worthy order.
For more information on what proofreaders do, see the Society for Editors and Proofreaders website.