You can easily do this from Preflight in Adobe Acrobat X.

1. Open Preflight. To do this, either press Ctrl-Shift-X, Cmd+Shift+X or click Tools -> Print Production -> Preflight (you may have to add the "Print Production" menu to the tools menu, do this by clicking the small panel button in the top right corner of the tools pane).
2. In Preflight, expand the PDF/A menu.
3. Click the "Remove PDF/A information" fix.
4. Click the "Analyze and fix" button in the corner.
5. Pick a place to save it to. Done!