I remember doing school assignments where I’d use different fancy fonts for each heading and changed the text to suit the amount of information in each section, and so on – and I was proud of being so versatile! But looking back (or at children’s work now) I can see that it looks childish and puts the focus on the fonts rather than the content. It isn’t very professional to give the impression you are trying to minimise the content!

As a general rule, it is better to stick to one font style and size in a single document. It is consistent which makes it easier to read (the eye doesn’t have to keep adjusting to different fonts) and it also looks clean and professional. And to be honest, it is also easier to prepare than swapping fonts all the time!

The common exceptions in font sizes would be:

• heading and sub-headings are often a little larger than the text font
• labels on diagrams and tables are often smaller to work with the labelled items
• the ‘fine print’ such as a disclaimer, a copyright notice or unsubscribe information – this text can be smaller but it must still be big enough to easily read so less than 8 point is getting too small in most cases. I recently edited a document which had footnotes to a table in a 7 font and it was too small to read and also looked out of place amongst the 11 font table and general text.
• fonts within an ad design may show more variation, but be careful to not overdo it

If you are tempted to change font sizes to break up a chunk of text, consider bullet points, italics, bold, more paragraph breaks and page layout as alternatives.