*pageto its page number,
*x0, *y0to its upper-left corner,
*x1, *y1to its lower-right corner, and returns 1. If there is no selection, this function returns 0.
The coordinates of the upper-left and lower-right corners are in the
PDF file coordinate space - they are not screen pixel
coordinates. This means that changes in zoom or rotation will not
affect the rectangle described by specific values of the four
coordinates. See the
pdfConvertPDFToWindowCoords2 for conversion
to window coordinates.