The line height for drawing text.
This property determines the size of text that is added to the
document using methods like AddText.
The font size is measured in the current Units.
You should prefer use of the XTextStyle.Size
property, to which the FontSize property is simply an integer
accessor. Assigning a value to the FontSize is exactly equivalent
to assigning it to the XTextStyle.Size.
Getting a value from this property is exactly equivalent to the
int n = (int)(doc.TextStyle.Size + 0.5);