private void FillForm()
    {
        try
        {
            string pdfTemplate = @"C:UsersDiogoDesktopfilesIMTT.pdf";
            string newFile = @"C:UsersDiogoDesktopP.pdf";
            PdfReader pdfReader = new PdfReader(pdfTemplate);
            pdfReader.SelectPages("1");
            using (FileStream stream1 = File.Open(newFile, FileMode.OpenOrCreate))
            {
                PdfStamper pdfStamper = new PdfStamper(pdfReader, stream1); //stops here
                AcroFields pdfFormFields = pdfStamper.AcroFields;

                pdfFormFields.SetField("Nome.12", "TESTE");
                pdfStamper.FormFlattening = false;
                pdfStamper.Close();
                stream1.Close();
            }
        }
        catch (Exception msg)
        {
            string m = msg.Message;
        }
    }