Using C++ Plugin how do I get PDF document's page size?

I want to create an adobe plugin using C++ to validate PDF document's page size, for some reason my application only supports 'Letter' page which is of size 8 .50 X 11.00 inch.

I have created some simple adobe C++ plugins and went through samples but did not find any api\method to get page size. Please advice me how do I get this info using Acrobat 10 SDK.

Thanks in Advance