Each job is different so providing an exact quote for work is impossible without assessing the document in question. For example, proofreading a very tidy document will take less time than editing a document pulled together from multiple authors whose first language isn't English.
I charge by the hour, and the number pages I can get through each hour is determined by the amount of attention required. One page = 250 words.
As a guideline, proofreading could be done at a rate of 8-12 pages per hours, whereas developmental editing could be as slow at 4 pages per hour.
Send me a query and I will work up a quote. I will never charge more than I quote unless the scope of work changes, with your agreement.