Not to be outdone, Readdle updated PDF Expert — which is hands down the best PDF app on iOS — to version 5.1 and added:

The iPhone version is finally as powerful as the iPad one. Now you can create freehand drawings and figures, manage pages and merge PDFs, select annotation groups and edit them, share files via SMB, and mark your files with colors and stars. All that powerful functionality is wrapped into gorgeous flat design.

They also note they sped up the app, which is crazy because it was already faster than anything else.