When you say 'natural pine bits', do you mean from a tree surgeon, chipped up pine tree, or just the bark. The bark's pretty inert, whereas the chipped woody stuff will break down and might lower the fertility of the soil. However, NEITHER will alter much the pH. Even naturally falling pine needles don't acidify the soil, because, by the time they've fallen, they've dried, and any content is inert. Green needles, too, have been tested, and it makes little difference, as they are only very slightly on the acidic side. You can go for it, safely.