Do you know the Ph of your soil? It maybe naturally acidic.
I have never check the Ph of my garden. With 25 beds they all could be slightly different. I have no problem growing potatoes except for the occasional wireworm problem.
If I had to I would probabally use mir-acid by the miracle-gro co. Long time ago I found out that evergreen bushes like acidic soil and the concrete that was by the bushes was messing up the soil. Mir-acid really did a great number to fix them. JMHO
I guess stubby didn't see this was the organic forum. Miracid is NOT organic...
Sulfur is the usual tool to shift towards acidic in the garden, but there are other ways... fungal dominated soils tend towards acidity, so a fungal compost or fungal compost tea would usually help to shift towards acidic (if there is a high calcium content, sometimes increasing the weak acid response can etch extra calcium out of the CEC, actually buffering and making things more base, but this is not that common).
However I agree with the groupthink that an acidic soil is not that important towards potato growing...
If you or family/friends drinks gallons of coffee, you may want to ask them to keep their grounds for you and add it. Or if you are close to someone who makes espressos and those types of drinks and such ask them to keep their grounds.
As many people said, you do not need it more acid. But I also think it depends on the potato you grow.