Acers don't need pruning on a regular basis. In fact, this can spoil their shape unless done carefully. However, if there is any dead wood it can be cut out anytime.
As for what's eating your Red Robin, I assume you mean Photinia 'Red Robin'. Can you tell me a little more? Add comments below in the 'add comment' section and we'll try to help.

The extra info Volunteer is asking for is to do with quite what you mean by 'something is eating' - do you mean there are lots of holes? What kind of holes, ragged ones? Preceded by browning? at the edges of the leaves or all over? Tons of holes so that the plant looks completely ragged? Or just a few here and there? First thing I'd suggest is lay some slug pellets - these plants seem to be rather tasty for snails and slugs.

Photinia are generally pest free, though I have had some this year appearing to suffer with black spot, and little holes in the leaves, which a good spray with Rose Clear completely sorted out. It may be worth a try, especially on any new shoots. Slugs and snails tend to leave trails rather than individual holes. About your acer - if you want to lift it or reduce it, then my tree surgeon friend recommends whilst it is dormant during the winter. Clean cuts to each branch, ie cutters that cut rather than crush. He also says to cut back to a shoot to stop die-back, or cut right back to the next branch, stem etc., depending on the shape you are aiming for.

yeah thanks everybody the holes are here and there but up high (4 - 5 ft) didnt think slugs got up there its not completely ragged but i dont want it to get like that.
I'll try the rose clear Avkq thanks and I'll sort out the acer

Snails will get up there - they prefer the new leaves, they're more tender. If you suspect a fungal problem, make sure the Roseclear you use is one that treats fungus - the combined product they used to make is no longer available.

cheers bamboo i'm on snail watch

How exciting - nights outside with a torch when its damp...

Have seen snails 50ft up in trees ... They are amazing climbers, but not feeders that leave nice neat round holes. More likely to be a small beetle/aphid of some sort? Still ... rose clear worked on mine so may be useful to you as well. If I get it back next spring, and the rose clear works again, will let you know. Black spot is also common to photinia and it could be this? I treat them whenever I treat my roses.