Yes, you can grind pumpkin seeds.
I was blessed with a couple of bushels of pumpkins and other cucurbits from a neighbor. I did some internet searches to see if they could be milled and saw several saying no. I tried it anyway--because I am like that. I had no issues with my Kitchen Aid Grain Mill. #amazonaffiliate "As an Amazon Associate I earn a tiny percentage from qualifying purchases.”
I think one of the issues people are running into with grinding pumpkin and similar seeds is that they are not roasting them first. I initially had seasoned and roasted these to use as snacks. We ate quite a few of them. I later decided to grind the seeds to add to other recipes. Btw, roasting the seeds does not destroy the antioxidants. In fact, according to one study I read, it increases them.
In conclusion, roasting at certain temperature can increase the sensory and nutritional attributes of pumpkin seed. After roasting, the concentrations of total phenols, total flavonoids, and antioxidant properties of pumpkin seeds were improved, which indicated that roasting enhanced the biological activity and antioxidant properties of pumpkin seeds. -Source
