Flatten All of the PDF Form Fields in C#. The details of this gist can be found in this topic https://kb.aspose.com/pdf/net/how-to-flatten-pdf-form-fields-in-csharp/.

Flatten All of the PDF Form Fields in C#.cs

using System;
//Add Aspose.Pdf for .NET package reference
//Use following namespaces to flatten PDF form Fields
using Aspose.Pdf;
using Aspose.Pdf.Facades;


namespace FlattenPDFFormFields
{
    class Program
    {
        static void Main(string[] args)
        {

            //Set Aspose license before flattening PDF form fields
            //with the help of Aspose.Pdf for .NET 
            Aspose.Pdf.License AsposePDFLicense = new Aspose.Pdf.License();
            AsposePDFLicense.SetLicense(@"c:\asposelicense\license.lic");

            //create an object of Form class to initiate form field flattening 
            Form PDFFormToBeFlattened = new Form();

            //Bind the PDF file which contains the form fields to be flattened
            PDFFormToBeFlattened.BindPdf("SamplePDFFormwithFields.pdf");

            //Use FlattenAllFields method to flatten all of the fields in the 
            //PDF form loaded above
            PDFFormToBeFlattened.FlattenAllFields();

            //Save output PDF file with form fields flattened using Save method 
            //of Form object
            PDFFormToBeFlattened.Save("OutputPDFwithFlattenedFormFields.pdf");
        }
    }
}