There are two possible answers - The PageUp key or the Up Arrow key on the keyboard.
Always taking people up at speed,
This refers to the fact that the PageUp or the Up Arrow take you up
I do have two good friends who will take you down,
This refers to the PageDown and the Down Arrow keys on the keyboard
And another who takes you up too.
Both the PageUp and the Up Arrow keys take you up. This refers to the Up Arrow key if you are using the Page Up key as the solution; It refers to the Page Up key if you are using the Up Arrow key as the solution.
It is certain that I am key. Am I saying it right though.
Actually should be saying that "It is certain that I am a key". Hence the reference to saying it right.
I help people jump around docks. Oh, there must be something wrong with my tongue today
Actually should be saying that "I help people jump around documents". Hence the reference to something wrong with my tongue today.