ABCpdf .NET PDF Component Documentation - XHtmlOptions HttpAdditionalHeaders Property. Additional HTTP headers to send in the request.

using var doc = new Doc();
string url = "https://www.websupergoo.com/"; // assign appropriate URL
var request = (HttpWebRequest)WebRequest.Create(url);
request.CookieContainer = new CookieContainer(); // required for HttpWebResponse.Cookies
request.Credentials = null; // assign appropriate credentials
using (var resp = request.GetResponse()) {
  // cookieless Forms Authentication adds authentication ticket to the URL
  url = resp.ResponseUri.AbsoluteUri;
  var response = (HttpWebResponse)resp;
  if (response.Cookies.Count > 0) { // includes ASP.NET_SessionId
    bool needsCookie2 = false;
    var builder = new StringBuilder("Cookie: ");
    for (int i = 0; i < response.Cookies.Count; ++i) {
      var cookie = response.Cookies[i];
      if (!needsCookie2 && cookie.Version != 1)
        needsCookie2 = true;
      if (i > 0)
        builder.Append("; ");
      builder.Append(cookie.ToString());
    }
    builder.Append(!needsCookie2 ? "\r\n" : "\r\nCookie2: $Version=1\r\n");
    doc.HtmlOptions.HttpAdditionalHeaders = builder.ToString();
  }
}
doc.HtmlOptions.Engine = EngineType.MSHtml;
doc.HtmlOptions.NoCookie = true;
doc.HtmlOptions.PageLoadMethod = PageLoadMethodType.MonikerForHtml;
int id = doc.AddImageUrl(url);
doc.Save(Server.MapPath("HttpHeaders.pdf"));

Using doc As New Doc()
  Dim url As String = "https://www.websupergoo.com/"
  ' assign appropriate URL
  Dim request As HttpWebRequest = DirectCast(WebRequest.Create(url), HttpWebRequest)
  request.CookieContainer = New CookieContainer()
  ' required for HttpWebResponse.Cookies
  request.Credentials = Nothing
  ' assign appropriate credentials
  Using resp As WebResponse = request.GetResponse()
    ' cookieless Forms Authentication adds authentication ticket to the URL
    url = resp.ResponseUri.AbsoluteUri
    Dim response As HttpWebResponse = DirectCast(resp, HttpWebResponse)
    If response.Cookies.Count > 0 Then
      ' includes ASP.NET_SessionId
      Dim needsCookie2 As Boolean = False
      Dim builder As New StringBuilder("Cookie: ")
      Dim i As Integer = 0
      While i < response.Cookies.Count
        Dim cookie As Cookie = response.Cookies(i)
        If Not needsCookie2 AndAlso cookie.Version <> 1 Then
          needsCookie2 = True
        End If
        If i > 0 Then
          builder.Append("; ")
        End If
        builder.Append(cookie.ToString())
        System.Threading.Interlocked.Increment(i)
      End While
      builder.Append(If(Not needsCookie2, vbCr & vbLf, vbCr & vbLf & "Cookie2: $Version=1" & vbCr & vbLf))
      doc.HtmlOptions.HttpAdditionalHeaders = builder.ToString()
    End If
  End Using
  doc.HtmlOptions.Engine = EngineType.MSHtml
  doc.HtmlOptions.NoCookie = True
  doc.HtmlOptions.PageLoadMethod = PageLoadMethodType.MonikerForHtml
  Dim id As Integer = doc.AddImageUrl(url)
  doc.Save(Server.MapPath("HttpHeaders.pdf"))
End Using