I'm using Aspose.Pdf 6.8.0.0 (2012.03.01), .NET 2.0 version.
Validating the attached PDF document causes NullReferenceException. (Object reference not set to an instance of an object.).
http://share.m-files.com/aspose/Kasikirja_print_FIN.pdf
Sample code for reproduction:
string srcFilePath = "Kasikirja_print_FIN.pdf";
string logfilePath = Path.GetTempFileName();
Aspose.Pdf.Document pdfA = new Aspose.Pdf.Document( srcFilePath );
pdfA.Validate( logfilePath, Aspose.Pdf.PdfFormat.PDF_A_1B );
Hopefully you can identify the problem and fix this issue.