Note: these examples work in all modern desktop browsers, but results will vary in older desktop browsers and mobile browsers. As of iOS 9, none of these examples work properly in Safari for iOS.
<object> enables you to leave fallback content if the browser doesn't support PDF embedding.
<embed> approach is widely supported, but not everywhere. Unfortunately,
<embed> doesn't provide a mechanism for fallback content. If the browser doesn't support PDF embedding, the end-user sees nothing.
<iframe> approach is widely supported.
<object> with an
<iframe> fallback will reach the most users.