PDF Compression by iTextsharp

string pdfFile = @"D:\google.pdf";

PdfReader reader = new PdfReader(pdfFile);

PdfStamper stamper = new PdfStamper(reader, new FileStream(@"D:\google.pdf", FileMode.Create), PdfWriter.VERSION_1_5);

stamper.FormFlattening = true;

stamper.SetFullCompression(); 

stamper.Close();