How to write a plugin for Pages in Cocoa

I'm sure there should be a way to write a Plug-in for Pages, in Cocoa or C since applications like Endnote do have a plugin for Pages. But from what I understood from the Apple documents, the Plug-In or Bundle architecture is needed to create a plugin and also information like which is the default folder for the plugins. However, I couldn't make any progress until now because, I neither could find the protocol or any documents related to develop plugins for Pages. My intended Plugin is intended to help in aiding me in my Thesis writing. If anyone could help, I'll be very thankful.

Thanks in Advance,

Regards.