While creating .PDF documents requires expensive software, reading them only requires the free Acrobat Reader, which can be downloaded from their website. Since different computer systems have proprietary protocols for coding such things as paragraph formatting, font sizes, underlining, etc., this is a uniformly accepted means of transmitting text in a bare bones format. It means just text, with no fonts, emphasis, or anything else. Background The color behind the text. It can be white, yellow, purple, textured, marbellized, paisley, a logo, or anything else.
Good taste is called for here, as well as consideration of the readability of the text.
If your needs require it, you can rent advertising on other web sites. This can be especially useful if you choose a site that attracts the kind of person that might do business with you. In Internet marketing, exposure is important. It gets on visitor's nerves. The program you are using to look at this.