Fonts play a huge part in making the document a certain way. The file can look like a scientific paper, a romantic letter, or a child's play just by its fonts. One has to be careful of what fonts and font styles one use.
The safest font style and size for me that goes with almost all documents are making the document in Times New Roman or Arial and setting the size to 12. They mostly never give criticism or raise an eyebrow.
One of the ways to make a statement effective and visible is to make it bold, underlined, or in italics. I emphasize and bold those ideas or words if I want the reader to focus more on them, and it works great for everyone. Highlighting words and text is also another way to emphasize the importance.