Answered
Someone here at work is asking if it is possible to click a button and get an open dialog appear so he can choose another PDF to open? I have been looking but I sure can't find anything. I know I can set an action to open a specific document. He would like to be able to let users choose the file to open.
The other option is to use the app.browseForDoc method. The documentation shows an example of what you're asking about, but you'd have to add the code to a trusted function in a folder-level JavaScript file, which shouldn't be a problem. See: http://livedocs.adobe.com/acrobat_sdk/9.1/Acrobat9_1_HTMLHelp/JS_API_AcroJS.88.138.php