I will appeal to the next editor/proof reader to consider if "proofer" is a word. I suppose it depends on context.
The proper term is "Copy Editor", and they handle grammar, punctuation and word choices. 'Proofer' is someone who looks at the book when it's been printed and searches for printing errors.
Different editor types, they consist of:
I'm sure I'll be corrected by any actual editors, but here's the general lay of the land in editorville:
Developmental Editing - They get you started before you write your story, examining your ideas, plot, story outline, etc.
Substantive Editing - A "Content" editor who focus on content (instead of mistakes). They look for consistencies, plot holes, incorrect characterizations, etc.
Copyediting - What most of us think of as 'editor', the guy who looks for typos, grammar and punctuation.
Proofreading - The 'last stage edit' for old time publishers (the guy who looks for publication errors).
Proofreader may also cover alpha and beta readers. These are people you trust to tell you your poop smells like shit. They'll read your story and tell you whether it works or not (i.e. will it be well-received, or is it boring as shit?)