I am trying to highlight required fields on an existing PDF using iTextSharp in a .net windows application. I am having trouble highlighing a radiobutton list. I've used getappearancestates to find the correct values but when I use .SetFieldProperty(FieldName, "bordercolor", iTextSharp.text.Color.YELLOW, null); It is not reflected on the pdf. When I look at the properties on the PDF for the radiobuttonlist the yellow background color is there. Just not rendering. I'm using acrobat pro 9 to view the PDFs.