Hello there and thank you for using Ask Extension. 

The problem with pruning junipers is that new growth only comes from the growing tips. Any branches pruned back to the bare wood will not grow back.  You will only have a bare spot in that place.  

So, to answer your question, if you do a "hard prune," that area of the shrub will not grow back.  If you decide to shear your shrub, you will get dense growth on the tips of the shrub. This is great for a hedge, but the inside of the shrub will lose its scales (leaves) due to lack of sunlight. 

What we do recommend is time consuming.  You can thin the shrub.  Remember that anything you cut back to the bare wood will not grow back. However, if you are selective where you make your pruning cuts, the adjacent branches will fill into the thinner areas.  

Here is a really good article from CSU that explains this more fully.  Skip down to the section on "Juniper and Arborvitae."  

 https://static.colostate.edu/client-files/csfs/pdfs/pruning-evergreens.pdf

Here is an additional article from Michigan State which further explains what they call "thinning cuts." 

 https://www.canr.msu.edu/news/pruning_evergreen_shrubs

Good luck.