Using Javascript to access "Appearance Options" under Add Header

No. Acrobat JavaScript has no access to that kind of dialogs.
If you want, you can crop all pages using JS, but you will have to manually provide the values to it.

It is true that there's no direct way to scale a PDF from either the menus and toolbar or the JavaScript DOM. The shrink option on the adding headers and footers dialog is a kind of side feature, not a main feature.

Similary, there are a couple if different indirect ways to scale PDF pages using JavaScript. Probably the best way is to use the doc.addWatermarkFromFile() function.

Here's the technique:
1. Create a new blank PDF with the right number of pages, correctly sized for the new scaling.
2. Save a copy of the original file.
3. Alternately pull pages from the two copies of the original and apply them as watermarks to the new PDF, using the scaling arguments in the doc.addWatermarkFromFile() function.
4. Inbetween the application of a page as a watermark you'll need to rename the OCG that the watermark function creates.

This creates a new scaled PDF. This is an awkward and far from ideal methodology because of the way it changes the PDF internally. You could write a plug-in that performed a much more elegant scaling. But the point is that it works.

Thom Parker
The source for PDF Scripting Info
[url=http://www.pdfScripting.com]pdfscripting.com[/url]

The Acrobat JavaScript Reference, Use it Early and Often
[url=http://www.adobe.com/devnet/acrobat/javascript.php]http://www.adobe.com/devnet/acrobat/javascript.php[/url]

Then most important JavaScript Development tool in Acrobat
[url=http://www.pdfscripting.com/public/34.cfm#JSIntro][b]The Console Window (Video tutorial)[/b][/url]
[url=http://www.acrobatusers.com/tutorials/2006/javascript_console][b]The Console Window(article)[/b][/url]