Turn PDF upside-down:
CGAffineTransform aCgAffTrans = CGAffineTransformMakeTranslation(0,892); //here the whole PDF page height should be given
aCgAffTrans = CGAffineTransformScale(aCgAffTrans, 1.0, -1.0);
CGContextConcatCTM(aCgPDFContextRef, aCgAffTrans);
Your are providing some random height while some part gets turned down and others remains the same. So a mirror like effect appears.