Readdle has released a new update for PDF Expert 5, with a ton of new features. They have integrated the ability to use Zoom Writing on the iPad, which lets you zoom in on the page you are writing on and follows you as you move along the page.
PDF Expert 5 also has AirTurn support. AirTurn Bluetooth pedals allow you to turn pages of documents hands-free, which is great for musicians whose hands may otherwise be occupied rocking out.
Readdle has also improved the bookmark function, added iCloud Drive Support, and included the ability to lock the app with Touch ID instead of using a passcode.
You can download PDF Expert 5 for $9.99 on the App Store.