iTextSharp - Merging a Batch of PDF Byte Arrays

Question

I am using iTextSharp to fill a few fields on a pdf. I need to be able to combine a series of these pdfs into one single batch pdf file. Below I am looping through a SQL result set, filling the fields of the pdf with values corresponding to the current record, storing that as a byte array, and consolidating all of those into a list of byte arrays. I am then attempting to merge each byte array in that list into a single byte array, and serve that as a pdf to the user.

It seems to work, generating a single file containing presumably as many individual pages as were in my result set, but with all the fields blank on each page. It works as expected when using FillForm() to serve a single pdf. What am I doing wrong?

byte[] pdfByteArray = new byte[0]; 
List<byte[]> pdfByteArrayList = new List<byte[]>();
byte[] pdfByteArrayItem = new byte[0];

foreach (DataRow row in results.Rows)
{
    certNum = row[1].ToString();
    certName = row[2].ToString();
    certDate = row[3].ToString();
    pdfByteArrayItem = FillForm(certType, certName, certNum, certDate);
    pdfByteArrayList.Add(pdfByteArrayItem);

}

using (var ms = new MemoryStream()) {
    using (var doc = new Document()) {
        using (var copy = new PdfSmartCopy(doc, ms)) {
            doc.Open();

            //Loop through each byte array
            foreach (var p in pdfByteArrayList) {

                //Create a PdfReader bound to that byte array
                using (var reader = new PdfReader(p)) {

                    //Add the entire document instead of page-by-page
                    copy.AddDocument(reader);
                }
            }

            doc.Close();
        }
    }

pdfByteArray = ms.ToArray();
context.Response.ContentType = "application/pdf";
context.Response.BinaryWrite(pdfByteArray);
context.Response.Flush();
context.Response.End();

private byte[] FillForm(string certType, string certName, string certNum, string certDate)
{
    string pdfTemplate = string.Format(@"\\filePath\{0}.pdf", certType);

    PdfReader pdfReader = new PdfReader(pdfTemplate);

    MemoryStream stream = new MemoryStream();
    PdfStamper pdfStamper = new PdfStamper(pdfReader, stream);

    AcroFields pdfFormFields = pdfStamper.AcroFields;

    // set form pdfFormFields
    pdfFormFields.SetField("CertName", certName);
    pdfFormFields.SetField("CertNum", certNum);
    pdfFormFields.SetField("CertDate", certDate);

    // flatten the form to remove editting options, set it to false
    // to leave the form open to subsequent manual edits
    pdfStamper.FormFlattening = false;

    // close the pdf
    pdfStamper.Close();
    stream.Flush();
    stream.Close();

    byte[] pdfByte = stream.ToArray();

    return pdfByte;
}

Answer 1

Adding the line below after setting the value for the fields seems to have fixed it:

pdfFormFields.GenerateAppearances = true;