How to add watermark image in pdf file

You have to use itextsharp.dll for in ..
Here is some example for applying watermark in pdf.

iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(WatermarkLocation);
    img.SetAbsolutePosition(125, 300); // set the position in the document where you want the watermark to appear (0,0 = bottom left corner of the page)



    PdfContentByte waterMark;
    for (int page = 1; page <= pdfReader.NumberOfPages; page++)
    {
        waterMark = stamp.GetOverContent(page);
        waterMark.AddImage(img);
    }

You can follow below link for more details

http://stackoverflow.com/questions/2372041/c-sharp-itextsharp-pdf-creation-with-watermark-on-each-page[^]

http://www.bluelemoncode.com/post/2011/12/21/Using-iTextSharp-with-aspnet-to-add-watermark-in-pdf-file.aspx[^]

http://nilthakkar.blogspot.in/2013/12/itextsharpadd-watermark-to-pdf.html[^]


Regards,
AARIF SHAIKH