What, exactly, does a proofreader do?
A proofreader is not an editor. The proofreading job is limited to 1) ensuring that every word in the prepared book matches every word (as edited or revised) in the manuscript; 2) obvious grammatical problems, typos, or missing or repeated text is noted. In other words, the proofreader reads for consistency, but does not read for sense. That's an editor's job, which has, presumably, been done already. Proofreading is a meticulous job, making sure that the first proof matches the MS, the second proof matches the first proof with corrections or changes, third proof (if there is one), same procedure.
This is a list of competent proofreaders. Their rates are usually calculated by the number of pages.
Or, if you have a meticulous friend who is literate— try them. You might be able to work out a trade.
DOUGLAS J. MILLER, author of Jesus Goes to Washington. “Birdie: Thanks for the big part you had in this book.”
ELEANORE HILL, author of the Rhodora Prize novel,The Family Secret. “Hey, Birdie. You did it again. Great work.”
Sasha — Thanks for the good work — very thorough.