Aside from professional, on-the-job experience, the only way to get an advanced education in editing and proofreading is to seek out a certificate program. Online certification can facilitate this pursuit because you can complete a program from your own home and at your own pace. However, many certificate programs are considered graduate-level programs, and require you to hold at least a bachelor's degree before you can enroll.
Simon Fraser University
Vancouver-based Simon Fraser University offers a Certificate in Editing program that can be completed online or by in-print distance education. The program consists of 150 hours of instruction, 130 of which are dedicated to core courses in editing, proofreading, grammar and ethics. The program at Simon Fraser doesn't have any prerequisites; you don't need a bachelor's degree to enroll. You only need to possess "excellent command of the English language." They'll even allow you take individual courses without enrolling in the certificate program.
ACS Distance Education
The 600-hour Certificate in Editing and Proofreading course at ACS is accredited by The International Accreditation and Recognition Council. The program includes a course in Photoshop in addition to the other core courses in editing, proofreading and editing practice -- which covers the process a manuscript undergoes from writing to publishing. Electives in this online program range from Ethics and Information Security to Journalism Practice and even Children's Writing. ACS also offers students of the program opportunities to get experience working for a program-run online magazine. No prerequisites are required to enroll in this program.
Poynter News University
Florida-based Poynter News University offers a Certificate in Editing in partnership with The American Copy Editors Society. The program contains six required courses, each of which consists of interactive video instruction and an end-of-course assessment. Each assessment is a combination of 15 to 20 multiple choice and true/false questions, and each one allows you up to three attempts to pass with a score of 80 or higher. There are no prerequisites for this program, and ACES members get a 50% enrollment fee discount.
University of California San Diego
The Copyediting Certificate program at The University of California San Diego is open to all fluent English speakers -- no prior degree or diploma is required -- and is governed by the university's Department of Arts, Humanities and Language. This not a self-paced program, and takes approximately nine to 15 months to complete. The curriculum consists of four required courses: three in Copyediting and one Grammar Lab, along with six recommended courses that do not count toward the certificate. Students in the program are also invited to participate in a free, online information session.