I have a 4 1/2 foot Norfolk Island Pine whose branches are more than 5 feet across and no longer fit in the corner where it sits during the winter. Can I safely cut back the lateral branches by a foot or so without harming the plant?
These plants are generally not pruned because it spoils their natural growth form. Normally the only pruning that is done is to remove any brown tips and dead branches. These trees grow from the tips of the branches and the top so any pruning (including "topping" it) will remove the growth point and the tree will not grow anymore beyond the pruned end.
That being said, it is possible to prune the side branches back so that it fits into the corner better. Use sharp shears to do this. It is important to know that, more that likely, there will be no new growth from those branches again so the tree might look funny and lopsided. If possible, prune at a point where there are still side shoots coming off the branch so it will hide the cut to some extent otherwise the branch will probably remain an unbranched "stub" forever.