Do you want to visually convey to the audience for your document that it is a draft only? Or that the information is strictly confidential? You can do that with a watermark.
The example on the left shows what a watermark is. The watermark tells people something about the document. You can also use a picture watermark if you want it to serve as a type of branding. Watermarks are semitransparent in color, so they sit behind and don't divert people's attention from the document's content. They are for documents that will be printed.
Another sort of background, shown here on the right, is purely for decoration and is intended for documents you'd post to a Web site. You can add all sorts of colorful backgrounds, including solid colors, gradients, patterns, textures, and even pictures.
The goal is to liven up the page — but you don't want to make it hard to read.
See how to add watermarks and backgrounds.