Empty the shelf completely. Any uneven weight distribution could cause the shelf to tip when being moved.
Load an empty pallet onto the pallet jack by sliding the prongs into the holes at the bottom of the pallet. The pallet provides a larger surface for the shelf to rest on that makes it more stable when moved on the jack.
Move the pallet jack under the shelf so that the empty pallet is centered underneath it.
Raise the jack until the pallet touches the bottom of the shelf. Stop the jack.
Remove the screws or bolts that hold the shelf in place. It should not move when these are removed if the pallet is touching the bottom.
Raise the jack to move the shelf to the desired height.
Reattach the screws or bolts to secure the shelf in its new location.