Hi Ratter,
There seems to be a few plants out there that also share the common name of 'Umbrella plant', so I'm going to assume its a 'Scheffleria' that you have.
Yes, I think it would be best to wait until spring to prune it, they can be pruned fairly hard if needs be. Cut just above a node and a dormant bud should appear from an old leaf scar.
they can be cut back to about 6-8 inches, providing it has 4 or 5 nodes below where you've cut.
Its best grown in a medium light position and kept moist but DO NOT over water.
Please also bear in mind the the plant is poisonous to humans and pets.