Paperrater.com is a free paper proofreading service. You can paste any paper into the website, and it will correct any punctuation or basic writing errors you may have made.
Paperrater.com offers a menu so you can choose your level of education as well as the type of paper or piece of writing you are submitting for basic proofreading. The service does not perform complicated editing, but it will alert you to grammar and spelling errors, clichés and overly complicated vocabulary, and it will provide suggestions to fix some of these errors. The site will also check any sources cited in the paper and can detect signs of plagiarism.