iOS - Getting thumbnail of PDF document

We can get the thumbnail of any page of pdf document. The following example is getting the thumbnail of first page

            NSURL* pdfFileUrl = [NSURL fileURLWithPath:filePath];
            CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfFileUrl);
           
            CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);//for the first  page
            CGRect aRect = CGPDFPageGetBoxRect(page, kCGPDFCropBox);           
            UIGraphicsBeginImageContext(aRect.size);
            CGContextRef context = UIGraphicsGetCurrentContext();
           
            CGContextSaveGState(context);
            CGContextTranslateCTM(context, 0.0, aRect.size.height);
            CGContextScaleCTM(context, 1.0, -1.0);
            CGContextTranslateCTM(context, -(aRect.origin.x), -(aRect.origin.y));
           
            CGContextSetGrayFillColor(context, 1.0, 1.0);
            CGContextFillRect(context, aRect);
           
            CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, aRect, 0, false);
            CGContextConcatCTM(context, pdfTransform);

            CGContextDrawPDFPage(context, page);
           
            UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext();           
            CGContextRestoreGState(context);
            UIGraphicsEndImageContext();
            CGPDFDocumentRelease(pdf);