The documents page is where you can access the document editor and see every document that you've created. Documents auto-save as you're working on them, so you can always find them back in the documents tab. Providing each with a unique, descriptive name will help you find just what you're looking for when you need to reopen a particular document.
You can also stay better organized by assigning documents to specific tasks, which you can do from the documents page or in an open document in the document editor.
To create new documents, simply click the green plus sign at the top of the page. You can create unlimited documents, and you can find them all easily with the search feature at the top of the page.