I'm confused: if the data is vector to begin with, then the dimensions are largely irrelevant. Shrinking a vector artwork in Illustrator shouldn't change the file size of the data. (Not proportionally anyway, though you may get some optimization.)
IF the data is JPEG images (not vector, bitmap), then Photoshop is your best bet, and it has excellent automation capabilities for reducing the size of images.
Use the right tool for the job...Acrobat. But be aware, there's a limit
to how much you shrink the size of a PDF without destroying the quality.
This has NOTHING to do with InDesign and I suggest paying a visit to the
Acrobat forum for advice.
- You have to check where is highest amount of space used in the pdf? Are these images or structures you need or you don't need? Is it a profile? Use the audit function in the Acrobat Pro Optimizer dialog.
- When you know which part of the content of the pdf could be dismissed you can set up a properly pdf export setting or use a different export functionality to create pdfs like the export of interactive pdfs which will output smller pdfs.