for US citizens, all that's needed is a COPY of a marriage certificate. I don't know what you mean by "parchment style" certificate. where i'm from in the states, the certificate is printed out on plain white printer paper and notarized by the town it was issued. it is not "parchment" style. also, the US marriage certificate (at least in the state i'm from) is a 1 page document. there are no other "marriage documents" and divorce documents would be completely separate.
for us citizens, all that is needed in the application is a COPY of the marriage certificate that is recorded by the town/city the marriage took place in. there is no specific type of paper it needs to be printed on, and it does NOT need to be the original copy. the US instructions are clear about this.
what you posted as a link certainly is not what a marriage certificate from the US looks like, at least the one that is commonly issued by the town/city the marriage takes place in. it usually looks like a legal document, and has a lot more information on it. kindly refrain from posting confusing and misleading information.
to the original poster, all you have to do is go down to the town hall where you got married and apply for a copy of your marriage certificate. it is really easy to do, and doesn't cost very much. make a copy for the application, and keep the original for your own purposes. it will also be needed if/when you want to change your name or open a joint checking account with your husband before being a PR.