Print .pdf and .tif files silently without any pop-up

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C#

Am trying to print .pdf and .tif files using C# in windows application.Printing is done successfully.But my problem is Adobe reader is opening in background for pdf files and windows print dialogue opens for tif files.Actually i will run my method using a service.So these process should occur silently.What i have to do to avoid this .i am really in need of help.
Here is my code

public void PrintDocument(string filepath)
        {
            //PrintDialog pd = new PrintDialog();           
            printProcess.StartInfo.FileName = filepath;
            //Also tried usecellexcecution=false;
            //Redirect=true; something like this
            printProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
            printProcess.StartInfo.Verb = "Print";
            printProcess.StartInfo.CreateNoWindow = true;
            PrinterSettings setting = new PrinterSettings();
            setting.DefaultPageSettings.Landscape = true;                         
            printProcess.Start();
            printProcess.CloseMainWindow();
        }

Also i try to use RawprinterHelper suggested in MSDN.But it prints junk characters.