From my experience with renewing a Dominican passport, the answer was in the PP office that it cannot be renewed until it expires. We were in Sosua a year ago February, and her passport expired in November 2015. So, wanting to be on top of things we went to the office to renew it since we would probably not be back till after it's expiry. This is when we were told it must expire first, we were surprised, and yet not. So we just let it go. She just returned and had it renewed in May, but we had to get a "Carta de Ruta" for a one way passage back to the DR. This was much cheaper than renewing in Canada. This is my experience only and who knows if the expiry issue it true...but hope it may help.