So, it should be PDF/A-1b, right?
Theoretially it should. In practice MS Word 2007 does not produce / export completely valid PDF/A files
You can use third party PDF/A validators (e.g. preflight tool in Acrobat Pro) to verify this.
Please note that besides deep validation you can also use ‘pdftron.PDF.PDFA.PDFAComplicance’ to convert these files to fully compliant PDF/A
For sample please see the second code example in PDF/A sample: