Gostaria de converter um arquivo PDF para .GIF usando C # e magicknet.dll. Eu adicionei a referência à MagickNet Dll ao meu projeto.

MagickNet.Magick.Init();
MagickNet.Image img = new MagickNet.Image("d:/aa.pdf");
img.Write("d:/bb.gif");
MagickNet.Magick.Term();
img.Dispose();

System.Runtime.InteropServices.SEHException was unhandled by user code
  Message="External component has thrown an exception."
  Source="ImageMagickNET"
  ErrorCode=-2147467259
  StackTrace:
       at Magick.Image.{ctor}(Image* , basic_string\,std::allocator >* )
       at ImageMagickNET.Image..ctor(String imageSpec)
       at Test1._Default.Button1_Click(Object sender, EventArgs e) in C:\Users\PANKAJ\Documents\Visual Studio 2008\Projects\Test1\Test1\Default.aspx.cs:line 31
       at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
       at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
  InnerException: