pdf to image in mvc is not working

Could not load file or assembly 'libpdf.DLL' or one of its dependencies. The specified module could not be found.

public string imagegen()
       {
           using (FileStream file = System.IO.File.OpenRead(@"..\path\Content\PDF\ApplicationForm_10.pdf")) // in file
           {
               var bytes = new byte[file.Length];
               file.Read(bytes, 0, bytes.Length);
               using (var pdf = new LibPdf(bytes))
               {
                   byte[] pngBytes = pdf.GetImage(0, ImageType.PNG); // image type
                   using (var outFile = System.IO.File.Create(@"..\path\Content\PDF\file.png")) // out file
                   {
                       outFile.Write(pngBytes, 0, pngBytes.Length);
                   }
               }
           }

           return "";
       }