Add signature to all pages of pdf

//reference https://gist.github.com/tempire/0bd8cb78290aa9bc6adf
func addSignature(_ signature:UIImage, onPDFAt path: String) {
        
        let pdf = CGPDFDocument(NSURL(fileURLWithPath: path))!
        
        let pageCount = pdf.numberOfPages;
        
        UIGraphicsBeginPDFContextToFile(path, CGRect.zero, nil)
        
        for index in 1...pageCount {
            let page = pdf.page(at: index)!
            let pageFrame = page.getBoxRect(CGPDFBox.mediaBox)
            
            UIGraphicsBeginPDFPageWithInfo(pageFrame, nil)
            
            let ctx = UIGraphicsGetCurrentContext()!
            
            ctx.saveGState();
            ctx.scaleBy(x: 1, y: -1);
            ctx.translateBy(x: 0, y: -pageFrame.size.height);
            ctx.drawPDFPage(page);
            ctx.restoreGState();
            
            signature.draw(in:  CGRect(x: 492, y: 652, width:100 , height: 100))//change accordingly
            
        }
        UIGraphicsEndPDFContext()
    }