How to add a form field to an existing pdf with itextsharp?

Question

How to add a form field to an existing pdf with itextsharp?

I have an existing pdf document, I\'d like to add form fields to it without creating a copy and writing o

Answer 1

I struggled with this for awhile so figured I'd post the Question & Answer

Using the PdfStamper itext class is the key. (I guess this does make a copy but it's much cleaner than using the itext PdfCopy classes).

public void AddFormFieldToExistingPDF( )
{
    PdfReader reader = new PdfReader(@"c:\existing.pdf");

    FileStream out = new FileStream(@"C:\existingPlusFields.pdf", FileMode.Create, FileAccess.Write);

    PdfStamper stamp = new PdfStamper(reader, out);           

    PdfFormField field = PdfFormField.CreateTextField(stamp.Writer, false, false, 50);

    // set a field w/some position and size
    field.SetWidget(new iTextSharp.text.Rectangle(40, 500, 360, 530),
            PdfAnnotation.HIGHLIGHT_INVERT);

    field.SetFieldFlags(PdfAnnotation.FLAGS_PRINT);
    field.FieldName = "some_field";

    // add the field here, the second param is the page you want it on
    stamp.AddAnnotation(field, 1);                        
    stamp.Close();
}