This option is not set by default. When this option is not active, the text box in the window will print with the same size as you can see it in the window. This means that if there is more text that fits on the visible text area, it will not print (The text will be truncated).
If you tick this option, the text box will expand vertically as long as it's needed to show the whole content of the text field.
You should have the Move controls on expand text or list option activated to adapt your printout to the new size of the text box.