无法使用WebClient下载PDF

Question

我们有一个访问外部API以获取和下载PDF文件的过程。这是过程：

using (var client = new WebClient())
{
    client.BaseAddress = add;
    client.Encoding = System.Text.Encoding.UTF8;
    client.Headers[HttpRequestHeader.ContentType] = "application/pdf";
    client.Headers.Add(HttpRequestHeader.Authorization, "Basic ");
    JObject jobject = generateReportPDFRequest(report.ReportID);
    //string tst = jobject.ToString();
    string result = client.UploadString(add, "POST", jobject.ToString());
    if (!string.IsNullOrEmpty(result))
    {
        retval = AddReportPDF(reportid, Encoding.ASCII.GetBytes(result));
    }
}

public static JObject generateReportPDFRequest(string reportid)
{
    try
    {
        // create the object
        JObject jsonRequest = new JObject();
        // add version property
        jsonRequest.Add("version", "1.0");
        // add content object
        JObject content = new JObject();
        JObject repid = new JObject();
        content.Add("customer-report-id", @"" + reportid + @"");
        content.Add("content-type", "application/pdf");
        JObject reportRequest = new JObject();
        jsonRequest.Add("content", content);
        return jsonRequest;
    }
    catch (Exception e)
    {
        string mess = e.Message;
    }
    return null;
}

我正在尝试使用Encoding.ASCII.GetBytes（结果）进程获取PDF，该进程将返回WebClient上传字符串帖子。流转换为字节数组并保存到数据库中。但文件是空的。

我有一个人告诉我，我将文件保存为版本1.6，下载的是版本1.4。如果这是问题，我该如何定义PDF版本？如果没有，我如何正确获取这些PDF文件？