All projects go through four editing stages:
Substantive/structural editing: Clarify and reorganize a document for content and structure.
Style editing: Clarify meaning, eliminate jargon, create polish and flow.
Copy editing: Edit for grammar, spelling, and punctuation. Check for consistency of mechanics and for internal consistency of facts.
Final Proofreading: Check page proofs of formatted, edited material for adherence to design and for minor, mechanical errors in copy (such as spelling mistakes or small deviations from a style sheet).
My standard rate is $45 per hour, payable upon completion of the project. For large projects I may ask for a deposit before starting.
For academic essays, this usually works out to $14-$18 per page. This is an estimate only and it can vary depending on the complexity of the subject and on the current condition of the manuscript.