Main text screen contains text view and is starting point for your work.

Page Up/Down buttons (pointed by blue arrow) offers easy navigation through text by moving text one page up or down.

Bottom Bar Button (pointed by red arrow) displays bottom menu with icons for contents, search, etc.

Swipe to Left/Right shows some other page, like contents or search, depending on settings.

Long tap on text will select part of the text and offers contextual menu.

History buttons - when applicable, history buttons are displayed in top left and top right corners of main text screen.

Left context menu - click on free space between text and left border of display will present the contextual menu with options: