The message that we want to put through is the most important part of any document. But how we do it, plays also a great role in the way the message will be conveyed. Fonts faces, sizes, and colors may radically change the way the reader perceives and ingests the content.

Sans-serif fonts, like Arial or Verdana, are universally used in electronic publications intended to be read on-screen due to the nature of electronic displays.

Serif font families are traditionally used in print media, making reading from paper easier and faster. The basic print text is usually black on white, but modern printing techniques and electronic media made room for a more diverse approach to color in documents. 

Monospaced fonts, like Courier, are often associated with computer terminals and are usually used to represent code listings and machine printouts.

Font colors and background colors are used to draw attention and highlight parts of the text, but should be used with caution, as using similar colors may produce unreadable results. A properly chosen set, however, will greatly improve text visibility and readability and may be used as an accessibility aid.

Custom text and background colors may be used to create infoboxes or quotations.

Text size may also play important role in driving the reader's attention.

Large text size would generally be used for important data, something, that really needs to stick out.

Fine print and tiny letters would rather provide some additional information, not necessarily the most important or interesting. Or one that we do not want to expose too much for some reason.