<p>To transpose a whole region at once, you can access the "transpose" dialog, by right clicking a region ><em>name_of_the_midi_region</em>> MIDI > Transpose...</p>
<p>This very simple dialog allows to choose either a number of semitones to add or substract to all the notes inside the region, and/or for more significant changes, octaves (12 semitones).</p>