"Hello,
I would be delighted to assist you with your project. I'm a native English-speaking proofreader and copy editor with more than 20 years of experience in a variety of industries, including academia, law, medicine, and fiction. I've also edited many documents in Australian and British English.
If you'd like to attach the document, I can give you an accurate estimate.
Thank you for your consideration. I look forward to hearing from you.
Regards,
Abby"