PdfDesign.cs

 public void Deneme(string filename) 
        {
            // variables            
            var pathin = Path.Combine(
                         Directory.GetCurrentDirectory(),"wwwroot",
                         filename);

            string pathout = Path.Combine(
                             Directory.GetCurrentDirectory(),"wwwroot/exported",
                             filename);

            var ImagePath = Path.Combine(
                            Directory.GetCurrentDirectory(),"wwwroot",
                            "nova-logo.png");

            //create a document object
            //var doc = new Document(PageSize.A4);
            //create PdfReader object to read from the existing document
            PdfReader reader = new PdfReader(pathin);

            //select two pages from the original document            
            reader.SelectPages("1-4");
            //create PdfStamper object to write to get the pages from reader 
            PdfStamper stamper = new PdfStamper(reader,new FileStream(pathout,FileMode.Create));            
            // PdfContentByte from stamper to add content to the pages under the original content
            //PdfContentByte pbunder = stamper.GetUnderContent(1);
            //add image from a file 

            var pages = reader.NumberOfPages;

            for(int i = 0; i < pages; i++) {

                Image logo = Image.GetInstance(ImagePath);
                //logo.ScalePercent(24f);
                logo.Alignment = Element.ALIGN_CENTER;
                logo.Alignment = Element.ALIGN_RIGHT;
                //logo.SetAbsolutePosition(72,72);
                //logo.SetAbsolutePosition(0,0);            
                logo.SetAbsolutePosition(reader.GetPageSize(i + 1).Width - 36f - 72f,reader.GetPageSize(i + 1).Height - 36f - 216.6f);

                PdfContentByte pbunder = stamper.GetUnderContent(i + 1);

                //add the image under the original content
                //pbunder.AddImage(logo,logo.Width / 2,0,0,logo.Height / 2,0,0);
                pbunder.AddImage(logo);
            }

            //close the stamper
            stamper.Close();
        }