Rick Borstein has posted an action for Adobe Acrobat to this page, which you can use to convert PDF/A archive files to the standard PDF format. The action will convert multiple files en masse.
The action uses Acrobat's Preflight functions. In Adobe Acrobt XI Pro these are found in the Tools menu in the Print Production section.
On the Profiles tab you'll see a function to remove PDF/A information.
Borstein's action allows for this Preflight function to process multiple PDFs. Borstein has posted instructions on how to install the action which can be downloaded as a PDF. The actual action .sequ file is embedded in the PDF file. You access it by clicking on the paper clip icon on the left. Just save the .sequ file on your hard drive and then double-click on it from Windows Explorer to install it.
If you don't have any PDFs open when you activate the action, 'Remove PDFa Information' from the Action Wizard menu it will prompt you add multiple files in the second step.