type of soil
It is not any acid in the soil that will harm your euonymus, it is the roots of the pine. Pine trees do not really acidify the soil and you usually rake up the needles, which do not do much to the acidity of the soil, anyway. Pines have very superficial roots that are thirsty and they can out-compete most plants for available water (although you can over-water pines by making the soil very wet all the time). So the euonymus would probably suffer from lack of water. I would not advise putting it so close. Alternatively, you could supply the euonymus with extra water on a regular basis. Good luck.