Submit form button - can I only send one page of the document?

This cannot be done directly. But there is a way to get the same effect.

Add the single page version of your form as an attachment. The use a script on the submit button to open the attachment (silently), copy the appropiate form data into it, the submit that form and close it. 

There are some potential problems with this approach. If the PDF is signed or certified access to the attachement could be blocked. Copying a signature is problematic. Will only work on desktop version of Acrobat and Reader.