IPad also does it itself. It also has built a in reader and also annotation. While reading a pdf open up the menu and find “Markup”.
There you're given the most powerful tool on the iPad — a dedicated stylus. For the first time there's a dedicated way to insert a note or an image into an existing document. If you tap it in and get the note or the image in, then you're done. If you want to insert text back or an image back, you just click “Restore”. There are still plenty of things that are hard to do like copying or pasting text. And there will always be limitations with the way that PDF editing works on the iPad which is why there are several apps that do it better. But it's not perfect and there is an app that will let you do a few advanced editing and PDF creation tasks. Markdown is the app that uses Markup in an entirely different way where it's like a wiki. Instead of.