Jumpers are often the shortest way to move a player (after, maybe, a teleporter). It's an actor with a radius that throws the player in a given direction toward a given navigation point.
A jumper requires three actors : UJumpPad, UJumpDest, and UJumpPadEnd. Put the UJumpPad at the center of the pad, and the UJumpDest at the point the Jumper is AIMING. The point where the UJumpDest is will be the highest point of the pawn's trajectory in the air (see the diagram). In the UJumpPad's properties, under the Lift Exit tab, put something in Lift Tag Put the same thing in the UJumpDest's properties, Lift Center tab, in the Lift Tag field.
If you rebuild and test your map at this point, you will notice that the jumper is working. If you do right-click => View => Show path in the title bar of the 3D viewport, you will see that a path connects the UJumpPad and the UJumpDest. But if you add further pathnodes, the UJumpDest won't be connected to the other paths. To allow bots to play normally, add a UJumpPadEnd at the end of the jump, at the point where the players are supposed to LAND. In it's properties, Lift Exit => Lift Tag, put the same thing as you did previously for you UJumpPad and UJumpDest. Add other pathnodes, rebuild and test.
The UJumpPad has a UJumpPad tab in its properties with a few parameters you can use to fine-tune it's behaviour. The most important one is Jump sound where you can enter a sound that will be played when a player walks on the jumper (the sound of the jump boots is perfect for that). Other parameters include bForceFullAccuracy (pretty self-explanatory: aims perfectly at the UJumpDest, but may modifiy the speed of the jump), JumpZHeightModifier (Allows the mapper to modify the height of the jump: a negative value will make the trajectory less high, while a higher value will send the player higher in the sky), and JumpVelocityModifier (Allows you to modify the speed of the player in much the same way).
The Jumper will work online. Bots can use the Jumpers provided you set up a UJumpPadEnd for them. Otherwise, strange behaviour may happen (as they land outside of the paths). As the Jumper is a 227 feature, it can only be used on a 227 server or on a 227 installation of Unreal. It will make your map incompatible with previous versions of Unreal.
Bots seem to be quite incompetent with jumpers and will rarely use them, even when correctly set up. If you are in doubt, check the jumper in UnrealEd: If everything is set up as it should, the UJumpPad should be linked to the UJumpDest by a yellow line when selected. This was added in 227i.