Yes, you absolutely can stack jars. The rack between is important to keep the top jars from sitting directly on the lid of the bottom ones. This could prevent the air from being fully exhausted causing seal and safety issues (rare, but possible). The instructions you posted above are exactly right.

What are you canning?

Deanna

Probably means just 4 or 8 ounce jars as 12 ounce or pints would be too tall to stack in typical canning pots.

I asked about stacking jars to process last year and was told that you could only do that in a pressure canning.

There has never been any rule against it. What was likely said was that most BWB canners just are not deep enough for jar stacking - even pints. Plus then come with racks that would make it difficult.

If you are using smaller jars so that they can still be covered buy the 2" of water and have a rack that can separate them - fine.

Dave

Last summer was my first time canning. I only have plans to do tomatoes this summer & perhaps some apples(sauce, pie filling) this summer.
I thought about getting some half pint jars because sometimes you want just a bit more tomatoes for what you are making & a quart or pint is more than you need. So you end up with an open jar in the fridge.
Thought if I got another rack, then perhaps I could do pints & half pints in one batch. Or 2 sets of half pints in one batch. I think my pot would be big enough for that.
Don't have a set plan, but dreaming about what I can do this summer, lol.

I use a cake cooling rack for between the stacks. I also use it when I only have a small batch to use a smaller, deep pot.