Wrong point when touch after scroll a page

[maahi22]

Hi there,
when we open a pdf and touch a point it giving right point coordinates. by
-(void) documentViewController:(MFDocumentViewController *)dvc didReceiveTapAtPoint:(CGPoint)point
but after scroll a page it not provide the xact point . this give point under 768, but my page go around 900 deep. any suggestion.

Thanks in Advance.
maahi