If you hire a professional editorial service, its editors will determine what your manuscript needs: proofreading, simple copy editing, or a very heavy edit, called substantive or line editing. You might have an idea already about the state of your book, but here is a quick guide.
Proofreading happens after written material has been copy edited and put into page proofs, a final e-file, or a pdf file, just before printing. A proofreader provides a final check of the text for minor mistakes in spelling, punctuation, spacing, and so on, before the manuscript, article, ad copy, or web content is published. Then the proofreader returns the pdf file, the e-file, or the page proofs to the typesetter (compositor), who will make the changes indicated. Usually, the proofreader reviews the pdf again to ensure that the compositor made each change correctly.
For a light to medium copy edit, the copy editor will correct grammar, spelling, punctuation, capitalization, and problems with syntax; will ensure that singular pronouns represent singular nouns and plural pronouns, plural nouns; will put the work in proper manuscript format; will standardize notes, bibliographies, and reference lists; and will make style decisions based on the Chicago Manual of Style (regarding punctuation, source citations, numbers, capitalization, Latin abbreviations, foreign words, quotations, etc., etc., ad infinitum). The copy editor will take care of endless details that most authors are unaware of but publishers are passionate about.
This can verge on an almost total rewrite of the book, but it usually proceeds on an incremental, detail-oriented level. In addition to performing the tasks of simple copy editing, a good editor takes an active role in initiating changes. In a heavy edit, sentences will be polished and reworded to improve clarity and flow and to get rid of repetition, clumsy wording, an overuse of passive voice, and convoluted sentence structure. Facts are checked and corrected, sections may be rearranged if necessary, and subheads and chapter titles might be reworked to make them catchier, funnier, or more dramatic. If, in their writing, authors occasionally become argumentative, cite personal theories as facts, use too much slang where it is inappropriate, or have a blind spot about when their tone is no longer “reader-friendly,” a good editor will make suggestions to remedy these problems. In numerous ways, an experienced editor will point out problems the author has overlooked and will help authors find their voice, refine their vision, and bring their manuscripts to a more perfect state.
Many variables come into play when pricing an editing job:
An editing mill might offer a simple copy edit by a relatively new editor, and this could be good enough if your book is polished and well organized, due to your own editing. Conversely, a simple copy edit would be almost useless with a book that needs a major rewrite.
Simple copy editing, substantive line editing, developmental editing, or all of these combined? And that gets into how many hours it will take the editor to complete the project, based on how many words per hour he or she can edit?
Do you have a tight deadline? Will you need a fast turnaround? Will you add substantial amounts of new text when revising, which the editor will then need to edit? It's hard to predict the amount of revisions that will be necessary when a book needs developmental editing. The author won't realize the gaps in the story or the choppy flow until an editor points out problems. This advice could spark entirely new directions that the author must explore.
For more on pricing, see "Free Sample Edit, Price Quote for Your Project, and Editorial Fees."