ASP.. NET专用字体在pdf中不能正确显示

我试图在我的pdf中使用的私有字体不应该显示。我在他们的wiki上看过PDF的锐利样本，以及在线的例子，但无法用自定义字体显示它。有人能看到下面的代码有什么问题吗?

    PrivateFontCollection pfc = new PrivateFontCollection();
    pfc.AddFontFile(Server.MapPath(@"~'Content'Fonts'Exo-Regular.ttf"));
    XPdfFontOptions opt = new XPdfFontOptions(PdfFontEmbedding.Default);
    //I have tried both of these options:
    XFont pdfFont = new XFont(pfc.Families[0], 12, XFontStyle.Regular, opt);
    XFont exoFont = new XFont("Exo", 12);
    gfx.DrawString("Did you receive the product as ordered?", exoFont, XBrushes.Black, 50, 45, XStringFormats.Default);
    gfx.DrawString("Did you receive the product as ordered?", pdfFont, XBrushes.Black, 50, 60, XStringFormats.Default);