I have inherited some questionnaire type forms with PDF extensions. They were created w/o any thought or consideration to genertaing interactive data entry forms. When I finish converting them to their interactive equivalents using the 'Create New Form' from an existing document feature in Acrobat Pro 8 and Live Cycle Designer opens in design mode, it appears that every form that was intended as a check box to be entered by a human with a pen(cil) exists as a 'Rectangle' object in this kicked-up version of the document's. By the way, I noticed that the "Run Field Detectiion" radio button was greyed out and not available to me during this process. So I was forced to choose "Place Fields by Hand".
I found that clicking on the 'Type' allowed me to change them from 'Rectangle' to 'Check Box', but there did not appear to be any opp'y to adjust the size of the checkbox's size -- meaning that I found that the caption could be manipulated but not the size of the entered X or checkmark visible to the eye when selected.
1. Select all of the checkboxes. All should turn blue but one; that will be red.
2. Right click on the red one.
2. Look at the Appearance Tab. There are choices there for Font size, color, etc.
4. Choose what you'd like; and that change should be applied to all of your checkboxes.
Hope this helps...
Acrobat is probably the program I use most often and I'm learning more every day.