I seem to remember a *bug* with the artbox inside Illustrator. If you
open the PDF inside Acrobat and then go Advanced / Print Production /
Crop Pages / you can change the page geometry to overcome the problem.

Another option would be to run the 'Convert to PDF/X-1a' preflight/fixup
which should reset the page geometry.

However, if this doesn't work then try the print router already suggested.

Jon