I bought it on ebay. The only one of its kind with no down arrow and/or instructions. I'll ask the seller but I don't think that is going to give me a definitive answer.There won't be any "added pressure".
I assume that the fuel flow should be from top to bottom the way it is positioned in your picture.
BUT......if it is also supposed to be a water trap, flow and orientation is important.
Ask the people who you bought it from.
There should be some kind of clamp on all fuel lines. Over time,they will come loose without that.