Jeff,
People often use Dolomite lime to do that. Top dress with at least 1 tsp/gallon of medium. You can mix it with soil a bit but careful not to damage roots. It will absorb and trickle down as you water.
JD
Edit: By work the acid level down...I assumed you want to raise your ph? If I was mistaken...then my advice was invalid.
If you want to make your soil more acid (lower ph) then just ph your water a little lower then normal. It'll help but won't seriously a;lter soil ph.