I've been an English teacher for 15 years and proofreading has always been a part of my job, whether it be academic papers, articles, M.A. dissertations, Ph.D. thesis or IELTS essays.
What I will do is: - correct your spelling, grammar, and punctuation - slightly edit the text to make it sound more natural and improve the flow (see my extras) - make sure the font is consistent throughout the paper
What I will not do is: - add content or rewrite the contents of your paper - check the facts you included in your research or paper - format the paper
What you will get: - a clean copy of the text - a copy which includes all my comments and all the changes I made (using track changes)