PDF/A-3a conversion with document level attachment

Hello, we are evaluating PDFNet SDK, but we have following problem:
we use this code to test PDF → PDF/A-3a conversion:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using pdftron;
using pdftron.Common;
using pdftron.SDF;
using pdftron.PDF;
using pdftron.PDF.PDFA;

namespace _Test

class Program

static void Main(string[] args)
string output_path = @“D:!Home\TMP”;
string input_path = @“D:!Home\TMP”;
string pdf_file_name = output_path + “test.pdf”;
string attachment_file_name = “sample_image.png”;
//create PDF with attachment
using (var doc = new PDFDoc())
doc.AddFileAttachment(attachment_file_name, FileSpec.Create(doc.GetSDFDoc(), input_path + attachment_file_name,true));
//convert to PDF/A-3A
using (PDFACompliance pdf_a = new PDFACompliance(true, pdf_file_name, null, PDFACompliance.Conformance.e_Level3A, null, 10, false))
pdf_a.SaveAs(pdf_file_name + “_PDFA-3A_ByPdfNet.pdf”, true);


This code finishes without any error and resulting pdf “test.pdf_PDFA-3A_ByPdfNet.pdf” is successfuly validated by Adobe Acrobat XI, but the document level attachment “sample_image.png” in “test.pdf_PDFA-3A_ByPdfNet.pdf” has unknown size and cannot be openned.
Attachment in “test.pdf” (pdf file before conversion) is ok.

Thank you for assistance.