PdfModule.cs

public class PdfModule : IHttpModule
{
    public void Init(HttpApplication context)
    {
        context.PreRequestHandlerExecute += context_BeginRequest;
    }

    private void context_BeginRequest(object sender, EventArgs e)
    {
        var httpApplication = (HttpApplication) sender;

        if (httpApplication.Request.Params["Pdf"] == null)
            return;

        httpApplication.Response.Clear();
        httpApplication.Response.AddHeader("Content-Type", "application/pdf");

        var baseUrl = string.Format("{0}://{1}{2}/", httpApplication.Request.Url.Scheme,
            httpApplication.Request.Url.Authority, httpApplication.Request.ApplicationPath.TrimEnd('/'));
        httpApplication.Response.Filter = new PdfFilter(httpApplication.Response.Filter, baseUrl);
    }

    public void Dispose()
    {
    }
}