Context based Draw function, which does the actual rendering of annotations.

PDFDocView.swift

// Context based Draw function, which does the actual rendering of annotations.

override func draw(with box: PDFDisplayBox, in context: CGContext) {
        if( path == nil){
            return
        }
            
        let localPath = path.copy() as! UIBezierPath
       
        super.draw(with: box, in: context)
        
        // Draw a custom purple line.
        UIGraphicsPushContext(context)
        context.saveGState()
        
        localPath.lineWidth = stencilWidth
        localPath.lineJoinStyle = .round
        localPath.lineCapStyle = .round
        stencilColor.setStroke()
        localPath.stroke(with: CGBlendMode.sourceOut, alpha: 0.4)
        
        
        //localPath.usesEvenOddFillRule = true
        context.restoreGState()
        UIGraphicsPopContext()
    }