Greetings Norm:
Technically, you can top-prune trees; however, I don't know any expert who would recommend top-pruning as an aesthetic, cultural practice for shaping and forming trees. In fact, there are hundreds of pruning publications published by academicians who state that you should never top-prune a tree (granted, there is always the occasional exception, but this practice does come with consequences).
Please refer to this Idaho Extension Forestry publication for conifer pruning:
http://www.cals.uidaho.edu/edComm/pdf/bul/bul0644.pdf
Best of luck!
