PdfStamper stamper = new PdfStamper(reader, new FileStream(
                        outFile, FileMode.Create));
            AcroFields fields = stamper.AcroFields;
 
            // Befüllen des Ausgabedokumentes mit Daten
            foreach (string key in data.Keys)
            {
                // set form fields
                fields.SetField(key, data[key].ToString());
 
            }
 
            // flatten form fields and close document
            stamper.FormFlattening = true;
            stamper.Close();
            StartPdfReader(outFile);