Rotation feature is in View menu of the main window. To quickly rotate a PDF page, simply click your mouse on any area of the PDF page, and then use the following hot keys,
Rotate clockwise: [Ctrl] + [Shift] + [+]
Rotate counterclockwise: [Ctrl] + [Shift] + [-]
For example, if you want to rotate counterclockwise the left PDF page by 90 degree, you press [Ctrl] + [Shift] + [-] only once.
