Show and hide Dotted border around annotation

How to show and hide a dotted border around selected annotation like ink, rectangle and oval?
I want to remove annotation from pdf, but to do that I firstly want to show dotted border around selected annotation, to differentiate between selected annotation from non selected ones.

PDFPage
-(PDFAnnot *)annotAtIndex:(int)index;
this method return a PDFAnnot object.

And in PDFAnnot object ,there have
/**
* @brief get annotation's box rectangle.
* this method valid in professional or premium version
* @param rect fill 4 elements: left, top, right, bottom in PDF coordinate system
*/
-(void)getRect:(PDF_RECT *)rect;


then use cocoa method to draw
// CGContextStrokeRect(context, rect1);
// CGContextAddEllipseInRect(context, rect1);