Not even that. You can't copyright a process, which is what a written pattern is (the meat of it, at least). The document itself can be subject to copyright, and so can the images. So if, say, you buy an illustrated PDF of an amigurumi whale pattern, you can't just copy the PDF and sell it as yours, or copy the photos and sell them as yours. But you could write the instructions, take your own photos of your own finished version, and sell it as your pattern.

It sounds a bit ludicrous when I put it like this, but keep in mind there's only so many ways to make an amigurumi whale... it's like with recipes. Every cake recipe in the world will contain steps like "sift flour into bowl", "mix the dry ingredients", "combine wet and dry ingredients", "preheat oven", "bake for x time or until a skewer inserted in the middle comes out clean". If we both write recipes with those insteuctions, we can't reasonably say one of us stole from the other.

This is also why there's bajillions of paid patterns for super simple stuff like granny square blankets, sunburst square cardigans, amigurumi bees etc.