How to hide layers when merging multiple pdf documents - pdf

Question

I'm using iText 5 to fill existing pdf forms with content and then merge them into a single pdf. I also want to turn on/off layers, but after merging all layers are visible.
This code shows the problem without using existing pdf forms. I would like to hide layer two but it seems not working.
static void Main(string[] args)
{
byte[] pdfPage = CreatePage();
byte[] result = Merge(new byte[][] { pdfPage, pdfPage });
File.WriteAllBytes(#"c:\test1.pdf", result);
}
private static byte[] CreatePage()
{
Document doc = new Document();
MemoryStream ms = new MemoryStream();
PdfWriter writer = PdfWriter.GetInstance(doc, ms);
doc.Open();
PdfLayer layer1 = new PdfLayer("Layer 1", writer);
PdfLayer layer2 = new PdfLayer("Layer 2", writer);
PdfContentByte cb = writer.DirectContent;
cb.BeginLayer(layer1);
ColumnText.ShowTextAligned(cb, Element.ALIGN_LEFT, new Phrase("Layertext 1"), 100, 700, 0);
cb.EndLayer();
cb.BeginLayer(layer2);
ColumnText.ShowTextAligned(cb, Element.ALIGN_LEFT, new Phrase("Layertext 2"), 100, 600, 0);
cb.EndLayer();
layer1.On = true;
// turn off layer 2
layer2.On = false;
doc.Close();
return ms.ToArray();
}
private static byte[] Merge(byte[][] pages)
{
Document doc = new Document();
MemoryStream ms = null;
using (ms = new MemoryStream())
{
PdfCopy copy = new PdfCopy(doc, ms);
doc.Open();
foreach (byte[] page in pages)
{
PdfReader reader = new PdfReader(new MemoryStream(page));
PdfImportedPage imp = copy.GetImportedPage(reader, 1);
copy.AddPage(imp);
reader.Close();
}
doc.Close();
}
return ms.ToArray();
}