Ann Maris, daughter of George Maris

I am working on several Quaker lines.Ann Maris, daughter of Geroge Maris married 1690 to John Worrilow, son of Thomas Worrilow.
Where could I find and obtain a photocopy of the "marriage certificate"?there is one on-line, the Worrilow family page.However, there is no information of where the original is located, and the copy, is not all that clear.