Many people confuse copy proofreading and copy editing. So what is the difference and which do you need to hire?
A proofreader is someone who looks over your manuscript for grammar, punctuation and spelling mistakes. A proofreader should see your manuscript AFTER all the editing, and beta readers have made their suggestions (and you have made all your changes). Basically, they should see your manuscript when it is ready for publication. Their job is NOT to make revisions but to make corrections.
In the world of publishing paper books, a proofreader was one of the last to review the book. They would be looking at the final copy as it would print. If there were too many end-of-line hyphens in a row or a blank section break at the top of a page, they would correct those and other esthetic issues in addition to checking grammar and spelling.
Nowadays, as software improves, the need for someone to proofread for spelling and grammar errors diminishes. In fact, I have mentioned before that I don’t hire a proofreader but use the software Whitesmoke for my proofing needs. (NOTE: As of November 2016, Whitesmoke no longer works. Company may have gone out of business.) This is a comprehensive grammar checker that will blow away what Microsoft Word does. Of course no software can completely replace having someone proof your work.
Many proofreaders charge by the hour while others charge by the word. And many copy editors also offer proofreading as part of their services.
While proofreading is done at the end, an editor may work over long periods of time with a writer until the manuscript is perfected. It is a much more involved process that can take months. And while some may argue editing also refers to finding typos and grammar errors, editing involves one major factor that proofreading does not: content.
A copy editor reads your work and makes corrections so it follows the conventions of good writing. They can find flaws in your story or help you flesh out a sub-plot. They refine word choices and make sure the manuscript’s syntax is smooth. The copy editor may suggest reorganizing, recommend changes to chapter titles and call out lapses in logic or sequential slip-ups. They will ensure continuity through chapters and ensure dialog is believable.
If employing both, use an editor first and then the proofreader afterwards. Editors may charge by the hour, by the page or even by the word.