From Tracker Software PDF SDK
The Crop method crops the specified page to the specified rectangular area.
HRESULT Crop([in] RECT* pRect);
- [in] Pointer to RECT structure which defines the rectangular cropping area. If this parameter is NULL the function will do nothing. If it specifies an empty rectangle, or an rectangle that has no intersection with page's rectangle, function will fail.
Returns S_OK if operation was successful or error code in other cases.