Readdle has updated PDF Expert for iPhone and iPad, adding support for the Appel Pencil, along with full support for the 9.7-inch iPad Pro. With Pencil support, you can now swipe through pages with your finger while you're annotating them when you're using the Pencil.
The other important new feature with this update is Readdle Transfer. With Transfer, you can easily move documents back and forth between PDF Expert on iPhone, iPad, and Mac, which has also added support for the feature. Any annotations you make can be saved back to the original source of a document, or to the device on which those changes were made. Transfer works much like Apple's own Handoff feature, initiating device-to-device file movement, rather than going through a cloud service.
You can grab the update to PDF Expert for iPhone and iPad from the App Store now, while the update adding Readdle Transfer to the Mac app is available either on the Mac App Store or directly from Readdle if you purchased the app from them.