Saving documents in Pages

I am working on a document in Pages. I saved the document and called it, "1script." Later I call up this document and add more information to it. I save this new document as, "2script." I like to keep all previous versions however, when I save "2script," the original "1script" document saves the changes too. So I end up with two identical documents. I would like to retain each document to track how it evolves. Is there a setting to change this so I can create a new version(s) but still retain the old version(s)?