Printing PDF generate with Itext7 on a thermal printer Model:P80D

Question

I am trying to print a PDF to a thermal printer via Bluetooth connection in Xamarin Forms. Print text only works correctly. But when I send the PDF it prints with strange symbols. I don't know much about thermal printers, but I would appreciate any help.

This is the method that creates the PDF

public byte[] Invoice()
{
    using (MemoryStream stream = new MemoryStream())
    {
        //Creamos instancia de los objetos necesarios para construir la estructura del PDF
        PdfWriter writer = new PdfWriter(stream);
        PdfDocument pdf = new PdfDocument(writer);
        Document document = new Document(pdf, PageSize.A4);
        document.SetMargins(2, 2, 2, 2);
        PdfFont font = PdfFontFactory.CreateFont(iText.IO.Font.Constants.StandardFonts.HELVETICA);
        PdfFont fontTitulo = PdfFontFactory.CreateFont(iText.IO.Font.Constants.StandardFonts.TIMES_ROMAN);


        //Datos de la empresa, factura y del cliente a mostrar
        Paragraph cabecera = new Paragraph("FACTURA").SetHorizontalAlignment(HorizontalAlignment.CENTER).SetTextAlignment(TextAlignment.CENTER).SetFontSize(11);
        Paragraph saltoLinea = new Paragraph(new Text("\n"));

        string dataQR = "395410026|0|0|0|0|0";
        byte[] qr = generaQR(dataQR);
        ImageData imageDataQR = ImageDataFactory.Create(qr);
        iText.Layout.Element.Image imageQR = new iText.Layout.Element.Image(imageDataQR).ScaleToFit(80f, 80f);


        document.Add(cabecera);
        document.Add(saltoLinea);
        document.Add(imageQR);

        document.Close();

        byte[] pdfBytes = stream.ToArray();

        return pdfBytes;
    }
}

And this is the way I send to the thermal printer

public async Task Print(string deviceName, byte[] pdfBytes)
{
    using (BluetoothAdapter bluetoothAdapter = BluetoothAdapter.DefaultAdapter)
    {
        BluetoothDevice device = (from bd in bluetoothAdapter?.BondedDevices
                                    where bd?.Name == deviceName
                                    select bd).FirstOrDefault();
        try
        {
            using (BluetoothSocket bluetoothSocket = device?.
                    CreateRfcommSocketToServiceRecord(
                    UUID.FromString("00001101-0000-1000-8000-00805f9b34fb")))
            {
                bluetoothSocket?.Connect();
                bluetoothSocket?.OutputStream.Write(pdfBytes, 0, pdfBytes.Length);
                bluetoothSocket.Close();
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
}

Print result