Hulling pumpkin seeds - Possible? Easy?
Describing the only method I know, and hoping that somebody will come up with an improvement, because this one is quite time-consuming. 

First, clean your pumpkin seeds and toast them. They cling to the hull when they are raw. When toasting, it is preferable to use lowish temperature for a long time, so you can prevent strong taste changes and burning. If I remember correctly, it is also a good idea to let them cool them first, because they are more likely to break when hot, but 

When the seeds are ready, you want to pop them out of the shell. For this, hold a seed between your thumb and index finger. Apply pressure to the most prominent parts of the edge. 



Ideally, the pointed part of the hull will split along the edge, and the seed will fall out, or you will be able to squeeze it out. Even if it goes like that seed after, it is a slow, monotonous work. Often, the hull will refuse to split, or the seed will break within the hull, or it will cling to the hull and refuse to come out after it has split. And then there is no guarantee that you'll get the beautiful plump seeds you see in the supermarket, because carving pumpkins aren't bred for nice seeds, it can happen that yours are very small and thin and not a particularly good decoration. 

Conclusion: it is possible, but even if I had the seeds sitting around, I'd throw them out (or feed them to birds outside) and get hulled seeds for cooking, instead of spending half a day to get a handful of seeds out of their hulls. If it doesn't bother you, or if you can find a more efficient method, feel free to do it and share your process improvements here.