Checkbox Not Displaying

Hi,

I have a document whereby I require a checkbox to display an actual checkmark. 

The reason I've put that in bold and italics is because I'm finding it so incredibly frustrating because Adobe Sign will not allow me to do this. I'm at the point of giving up and just printing, manually checking and scanning instead.

The final document (once signed) is just displaying the checkbox filled in, with no actual checkmark.

Can anyone help?

I've attached a photo for demonstration (circled in blue):

Many thanks in advance for any help!