将PDF加载到UIWebView时发生内存泄漏

Question

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.webView.delegate = self;
    NSString *path = [[NSBundle mainBundle] pathForResource:@"Abtretung" ofType:@"pdf"];
    NSURL *url = [NSURL fileURLWithPath:path];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [self.webView loadRequest:request];
}

在模拟器上没关系，但在设备上有内存泄漏。