Annotations lost converting to PDF/A

Still evaluating aspose.pdf for PDF/A conversion. 

I have a simple pdf, annotated with "Drawboard PDF" application (windows store) and a pen device. Converting to PDF/A-2b or even PDF/A-1b, all annotations are lost! Highlights and pen writing.

No problem when converting the same document with Acrobat XI.

You'll find the sample file attached.

Thanks

Jerome