Evidently pansies like an acid soil, pH 5.4 to 5.8, but a friend of a friend, I'm told, had wonderful pansies because she put some lime on the soil every year. A paradox?
First, ordinary soil in the NW can range from 5.0 to 6.0 and if someone's added a lot of organic matter it can go lower. If they're growing vegetables, they've probably added some lime to bring the pH up to 6.5 or so, good for almost everything except potatoes.
But I'm growing pansies in my vegetable garden, with occasional lime, and they're doing much better than anywhere else. So I'd say add some lime here in the NW if you want to grow great pansies.
Of course, there are always soil meters, soil tester, all sorts of toys to play with. Not necessarily accurate. If you're really concerned about your vegetables, try a professional testing service. I have a really good soil testing meter, a Kelway, and I still prefer to watch the appearance of my plants.