Thanks to both of you for your replies. But I've tried it with a knife in every possible squar and it just cuts slices. Checked the handbook and it doesn't mention anything. Whole pumpkin doesn't work either.
Maybe it really was added in a more recent version...but I've been trying to make seeds with pumpkins on and off for a looong time. So I thought that the version to just put the pumpkin in the crafting grid might be outdated... LOL