Script that currently i used to secure the PDF file, so user when download it the PDF they will not able to Copy and modify the content for that PDF itself.
Here as below the script :
using (var stamper = new PdfStamper(pdfReader, ms))
System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
stamper.SetEncryption(null, encoding.GetBytes(“12345678”), ~(PdfWriter.AllowCopy | PdfWriter.ALLOW_MODIFY_CONTENTS), PdfWriter.STRENGTH40BITS);
You can also set as many PDF Restriction they have, here are the list below :