It is my understanding that when we ad a new article or preselling or sales page to our sites that our search results will be better. Is this also true when we update a page making changes it?
Making changes to a page will definitely have less effect than adding a new page. When you add a new page that is a whole new set of keywords that you might rank for. Also it is another set of internal links for some of your other pages. Adding a page won't have a huge effect though. You will see more effect by adding quality backlinks on a regular basis.