public void DrawButton(PdfFormField button, string caption, BaseFont font, float fontSize, float llx, float lly, float urx, float ury)
{
PdfAppearance pa = PdfAppearance.CreateAppearance(writer, urx - llx, ury - lly);
pa.DrawButton(0f, 0f, urx - llx, ury - lly, caption, font, fontSize);
button.SetAppearance(PdfAnnotation.APPEARANCE_NORMAL, pa);
}