Proofreading

What is a Proofread?
Commonly referred to as proofing, proofreading is a last review for lingering errors.
Unlike the 'proofread' that is understood in academia, publishing considered proofreading the last phase of editing, where only lingering errors might exist.
What Does Proofing Involve?
In academia, we are taught to have a "proofread" before we turn a final draft in, and in that process, any improvements that a reader might feel would be beneficial are mentioned.
In publishing, a proofread is a last read, after all phases of editing have been completed. This last read looks for lingering errors or omissions that commonly occur from the manuscript having undergone copy edits. Things like: a missing end quote, a missing punctuation mark, words that were accidentally smushed together because of an accepted track change correction.
A proof can also review whether minor things like chapter headings or book formatting is consistent -- although in cases of formatting, the proofreader isn't likely to fix formatting errors, just note them for the author.
I am extremely selective about the proofreading projects that I accept. Too often, CEs have been performed by under-qualified copy editors, which leaves me in a position of having to call that editor's work out as unprofessional. I will not put myself in that position.
If you received a Style Guide from your copy editor, I am more likely to accept a proofreading project.