GetSize:
LPDISPATCH GetSize();
Description:
Gets a page’s width and height in points.
Parameters:
Return Value
The LPDISPATCH for an AcroExch.Point containing the width and height, measured in points. Point x contains the width, point y the height.
单位是 点, 和英寸的 转换关系是： 点Points (1点 = 1/72英寸)
因此对于大小为（8.26 × 11.29 ）英寸的 PDF，返回值分别为：595 ， 842