[puffinstuff]

I didn't manage to prune plum tree last year.  Is it okay to prune now.  I know you're not supposed to prune until Summer to avoid leaf disease.  Any advice on pruning method would be appreciated!!

[Lardman]

I know you're not supposed to prune until Summer to avoid leaf disease. 

Is it okay to prune now. 

I think you've answered your own question. 

You can prune it any time you wish - it's your tree. But why do you want to prune it?  It's a bit early for summer pruning to promote good fruiting next season and to control the tree growth and just a bit late to encourage new vegetative growth for this season.