Work with PDF on Server

Thank you Tuhin and Daniel for your input.

Tuhin, I tried your suggestions but I can't get to override or update the continue fillable .PDF when creating the new one from the template and fill in the blank then save it ti does not carry the data over. 

This my code that does the update, it just creates a copy of the existing one without the extra data entered while continuing fillining the blank

public void UpdatePdf(string existingPdfPath, string pdfileName)
{
    string existingPdfilePath = existingPdfPath + pdfileName;
    string updatedPdfPath = existingPdfPath + "I-693_" + Guid.NewGuid().ToString() + ".pdf";
    using (FileStream pdfReaderStream = new FileStream(existingPdfilePath, FileMode.Open, FileAccess.Read))
    {
        using (FileStream pdfWriterStream = new FileStream(updatedPdfPath, FileMode.Create, FileAccess.Write))
        {
            PdfReader reader = new PdfReader(pdfReaderStream);
            PdfStamper stamper = new PdfStamper(reader, pdfWriterStream);

            AcroFields formFields = stamper.AcroFields;
            foreach (DictionaryEntry de in reader.AcroFields.Fields)
            {
                //sb.Append(de.Key.ToString() + Environment.NewLine);
                var fullname = formFields.GetTranslatedFieldName(de.Key.ToString());
                formFields.RenameField(fullname, Guid.NewGuid().ToString("N"));
                if (de.Key.ToString() != fullname)
                    if (!String.IsNullOrEmpty(de.Value.ToString()))
                    {
                        if (fullname != "form1[0].#pageSet[0].Page1[9].PDF417BarCode2[0]")
                        {
                            formFields.SetField(de.Key.ToString(), de.Value.ToString());
                        }
                    }
            }
            stamper.Close();
            reader.Close();
        }
    }
}

You can download the whole test project here -->https://netstair.com/src-sample/Test-iTextSharp.zip

Thank you for all your help.

Yes, it is possible to fill a PDF, save it to the server, and later modify or add data to it in an ASP.NET 4.7.2 WebForms application using iTextSharp .

using iTextSharp.text.pdf;
using System.IO;

public void FillPdf(string templatePath, string outputPath, Dictionary formData)
{
    using (FileStream pdfReaderStream = new FileStream(templatePath, FileMode.Open, FileAccess.Read))
    {
        using (FileStream pdfWriterStream = new FileStream(outputPath, FileMode.Create, FileAccess.Write))
        {
            PdfReader reader = new PdfReader(pdfReaderStream);
            PdfStamper stamper = new PdfStamper(reader, pdfWriterStream);

            AcroFields formFields = stamper.AcroFields;

            // Populate form fields with data
            foreach (var field in formData)
            {
                formFields.SetField(field.Key, field.Value);
            }

            // Flatten the form if you want to make it read-only
            // stamper.FormFlattening = true;

            stamper.Close();
            reader.Close();
        }
    }
}

• templatePath : Path to the original PDF template with form fields.
• outputPath : Path where the filled PDF will be saved on the server.
• formData : A dictionary containing field names and their corresponding values.

Instead of sending the PDF to the client, save it directly to the server's file system. You can use a folder like ~/PDFs/ for storing the files.

string serverPath = Server.MapPath("~/PDFs/");
string fileName = "ClientForm_" + Guid.NewGuid().ToString() + ".pdf";
string fullPath = Path.Combine(serverPath, fileName);

// Call the FillPdf method
FillPdf(Server.MapPath("~/Templates/Template.pdf"), fullPath, formData);

// Optionally, store the file path in the database for future reference
SaveFilePathToDatabase(fileName, fullPath);

 Retrieve and Modify the PDF

To allow users to modify the PDF later:

1. Retrieve the PDF : Fetch the stored PDF from the server.
2. Repopulate Form Fields : Use iTextSharp to reload the PDF and allow modifications.

Here’s how you can modify an existing PDF:

public void ModifyPdf(string existingPdfPath, string updatedPdfPath, Dictionary updatedData)
{
    using (FileStream pdfReaderStream = new FileStream(existingPdfPath, FileMode.Open, FileAccess.Read))
    {
        using (FileStream pdfWriterStream = new FileStream(updatedPdfPath, FileMode.Create, FileAccess.Write))
        {
            PdfReader reader = new PdfReader(pdfReaderStream);
            PdfStamper stamper = new PdfStamper(reader, pdfWriterStream);

            AcroFields formFields = stamper.AcroFields;

            // Update form fields with new data
            foreach (var field in updatedData)
            {
                formFields.SetField(field.Key, field.Value);
            }

            stamper.Close();
            reader.Close();
        }
    }
}

Serve the PDF to the User

When the user wants to view or edit the PDF, serve it to them via a download link or embed it in the browser.

Example:

protected void DownloadPdf(string filePath)
{
    Response.ContentType = "application/pdf";
    Response.AppendHeader("Content-Disposition", $"attachment; filename={Path.GetFileName(filePath)}");
    Response.TransmitFile(filePath);
    Response.End();
}

Here is the flow :