What do you mean by external? Generally speaking, Acrobat JavaScript has pretty good features for internet communication (SOAP and HTTP Get/Post). But it's heavily restricted when it comes to the local file system. Even more so when a script is executed from a document.
I'm a developer and have an application running on the same computer (under Windows). I'd like to create a PDF file which sends a simple message when I click certain links in the PDF... Can it be done? The application can be reached as a COM server, if that is any help.
Thom Parker
The source for PDF Scripting Info
www.pdfscripting.com
Very Important - How to Debug Your Script