To save your questions while making the document, click continue and your answers will automatically save. To save the whole document, click save after finishing all of the questions.
To edit an incomplete document, click the "begin/continue document" button and you can edit any of your answers. If you have completed your document and wish to make changes, click the gear button to the right of the document and click "edit document." You will then be able to go through and change any of your answers as needed.