When producing a tagged PDF (see Creating a Tagged PDF),
checkboxes are converted to an image for the rendered PDF. Alternate text is
automatically added to checkbox images as "checkbox is marked" or "checkbox is not
marked" based on the state of the chec box (selected or unselected). If not creating a
Tagged PDF, the Pi font is used for checkboxes. Figure 1. Example of Tagged PDF check box with Alternate Text
