I will do two hours of editing on your document / web page / assignment / proposal. If it has non-technical content and you're an English first-language writer, that's about twelve to fifteen hundred words. I'm very experienced with ESL writers, so could do just a bit less than that if English isn't your first language. Or it's technical stuff (I'll tell you my limits on that when you ask).
I'll correct grammar and suggest improvements in style, according to your intended readers.
I can work in MS Word (with tracked changes and comments). If you send me a PDF, I'll work a bit slower on inserting suggested changes. Text files are easy.