A tutorial, where the most common features of the app are shown, is online at the following link:
https://www.youtube.com/playlist?list=PL3VL6s-M7yoeFSHGs-Z2qJdVV_WcdMuy6

With the release of the latest version the videos are a little bit out of date: at this link you will find a short manual that shows how to use the buttons in the new format:
https://inkandpaper-app.github.io/website/SHORT_MANUAL.pdf

• Write on your Android device like you would on a sheet of paper.

• Six customisable types of pens with the best digital inking features are available.

• Insert in the most natural way typed texts, images, geometrical shapes in your pages.

• Select and move, zoom, rotate, stretch any object using your fingers.

• Control undo and redo actions with the undo/redo bar.

• Overlay objects and manage their opacity using layers.

• Take full advantage of an active stylus by configuring the erase methods.

• Work with close up writing mode on small screen devices.

• Use gestures to select or delete objects while you are writing.

• Set the background of any page by the import of JPEG, PNG and PDF documents.

• Create new notepads from the most common document templates.

• Save and load customised sets of colours, pens, typewriters.

• Organise your notes into library folders. Cut, copy and paste notepads and pages.

• Export and share documents in PDF, JPEG, PNG formats. The PDF format is entirely vector based.

• Backup and restore any section of the library in ZIP format.

Before purchasing, you can download the free trial version, which lacks PDF export feature, at this link:
https://play.google.com/store/apps/details?id=com.inkandpaper.trial