Need Javascript for shrinking document

Scaling can also be achieved using the Preflight tool, which can be triggered using a script. However, it has to be a fixed size. It can't automatically decide what size to scale the pages to based on the white margins of the page, like the Add Header and Footer tool can.

Yes, there is a way to do this. There is no functionality in the Acrobat JavaScript model for directly scaling page content. But there are a couple of techniques. Both button fields and watermarks scale images. The watermark technique is the simplest, but like most complex operations in JS, it has a weirdness.

Create a new page of the desired size. The page dimensions must of course maintain the original aspect ratio. Then use the watermark function to place the source page content over new page.  The issue with this technique is that watermarks are also OCG layers. To use this technique to scale all pages in a document will require renaming the OCG layer.

You can read about OCGs and the watermark function here:

http://acrobatusers.com/tutorials/create_use_layers