Acrobat not reading new bouding box (Bbox)

Hi,

I am trying set and get ( this.getPageBox("BBox"); ) bouding box in acrobat javascript. I know that Bbox is readyonly and cannot set it manually. But I am putting some invisible white text at the bottom of page and making bouding box large. 

The problem is that acrobat does not read the new larger bouding box if the document edited stay open but detect changes when the same document is closed and reopened again. 

Can someone please help me in how to solve this?

Thank you
Arvind