Rotate multiple pdf/a files using Adobe Acrobat Pro

I have about 100 pdf files that I need to rotate to the left by 90 degrees.  I presume many if not all of them are stored in PDF/A mode a.k.a. PDF/Archive mode.  I have a workflow to rotate pdf/a files using my copy of Adobe Acrobat Pro version 9 however, the workflow I have is rather cumbersome.

1. Open the pdf/a file in Adobe Pro 9
2. Go to Advanced -> Preflight -> pdf/a -> Remove pdf/a.
3. Save the pdf - so that it is no longer in pdf/a mode.
4. Reopen the pdf file.
5. Now Adobe will let us rotate the document under Document-> Rotate Page.
6. Save the pdf - technically this should be saved as a pdf/a again.

Questions:

1. This workflow works for rotating a single pdf/a document.  However it is rather cumbersome.  Is there a quicker solution?
2. I have seen some indication that it is possible to rotate many pdf documents 90 degrees to the left at once.  However, will this work for pdf/a documents?  In addition is this feature available in Adobe Acrobat Pro Version 9?

Thanks