string outputFolder = @"C:\Users";
             string inputFile = @"C:\"
             var xDpi = 300; //set the x DPI
              var yDpi = 300; //set the y DPI
            var pageNumber = 1; // the pages in a PDF document
(var rasterizer = new GhostscriptRasterizer()) //create an instance for GhostscriptRasterizer
            {
        rasterizer.Open(inputFile); //opens the PDF file for rasterizing

              //set the output image(png's) complete path
         var outputPNGPath = Path.Combine(outputFolder, string.Format("0.png"));

           //converts the PDF pages to png's 
              var pdf2PNG = rasterizer.GetPage(xDpi, yDpi, pageNumber);

              //save the png's
         pdf2PNG.Save(outputPNGPath, ImageFormat.Png);

         Console.WriteLine("Saved " + outputPNGPath);

              }