Teachers, friends, and family members do not always make the best editors. You need an unbiased eye on your work someone who is more interested in crafting good sentences than in saying nice things about your work. Every book, even those written by Nobel Prize winners, needs editing and proofreading. These are two different processes and have two distinct purposes. Editing is done while the book is in manuscript form before design and layout.
Editors can work on hard copy or electronic files.
Proofreading is performed after typesetting on the finished, typeset pages. This is a quick read. The major editing was completed previously by the editor. At this point, every sentence should be lean and working efficiently, and the proofreader shouldn t have to perform reconstructive surgery. Proofreading is done on the finished pages because the proofreader will look at headers, footers, headlines, subheads, page numbers, bulleted lists, paragraph indention, and other formatting elements.