here. We can save you some time -- a single book title or movie title cannot be registered at the U.S. Patent and Trademark office. You can, however, register a title that's part of a series, for example, the Up series. (Here's an article with some workarounds for acquiring trademark protection for single movie titles.)
Branding. We remember when "to brand" meant to burn the flesh of an animal to indicate ownership. Ouch! Nowadays, of course, it refers to all kinds of marketing stuff typically related to a product or service line. In addition to product branding, there's personal branding, faith branding, nation branding, and employer branding. We're going to assume that branding your documentary means that you want to expand your "product line" to as many happy customers as possible. We couldn't tell you how to do that and if we could, we'd probably be doing something else.