sorry for the late reply. Your posting did scroll out of focus in 
Mail and I only found out that there's no reply to your post now that 
I looked over the forum directly on the website.

Regarding your question:

The "Page up" and "Page down" keys are already triggered by the 
Preview behaviour for its "Next page" and "Previous page" actions. By 
default they are mapped to the left and right buttons on the remote.

Hope that helps.

Best regards, 
Felix