PDF/A-Document saved from Word 2007 noch valid?

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 :frowning:
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:
http://www.pdftron.com/pdfnet/samplecode.html#PDFA