static void EraseJS(Obj js)
{
    if (js.IsString())
    {
        js.SetString("//sanitized");
    }
    if (js.IsStream())
    {
        js.SetStreamData(System.Text.Encoding.ASCII.GetBytes("//sanitized"));
    }
}

static void CheckDictOrStream(Obj dict)
{
    Obj js = dict.FindObj("JS");
    if (js != null)
    {
        EraseJS(js);
    }
    var diter = dict.GetDictIterator();
    for (; diter.HasNext(); diter.Next())
    {
        Obj current = diter.Value();
        if (current == null) continue;
        if (current.IsIndirect()) continue; // skip
        if (current.IsArray())
        {
            CheckArray(current);
        }
        if (current.IsDict() || current.IsStream())
        {
            CheckDictOrStream(current);
        }
    }
}

static void CheckArray(Obj arr)
{
    for (int i = 0; i<arr.Size(); i++)
    {
        Obj item = arr.GetAt(i);
        if (item == null) continue;
        if (item.IsIndirect()) continue;
        if (item.IsDict() || item.IsStream())
        {
            CheckDictOrStream(item);
        }
        if (item.IsArray())
        {
            CheckArray(item);
        }
    }
}

static void SanitizeDocument(PDFDoc doc)
{
    if (doc.GetTrailer() == null) return;
    CheckDictOrStream(doc.GetTrailer());

    SDFDoc Sdoc = doc.GetSDFDoc();
    for (int num = 1; num < Sdoc.XRefSize(); num++)
    {
        Obj current = Sdoc.GetObj(num);
        if (current == null) continue;
        if (current.IsFree()) continue;
        if (current.IsArray())
        {
            CheckArray(current);
        }
        if (current.IsDict() || current.IsStream())
        {
            CheckDictOrStream(current);
        }
    }
}