Pollination is important for fruiting plants that require a pollinating partner. Self fertile plants are identified in the specifications table on the product pages and do not require a pollinating partner. Although, they would likely produce higher yields if there is one present.
For most common fruiting species such as apples, pears and stone fruit, it is unlikely that there will not be a pollinating partner within the radius required already.
For those plants that do require pollination, you can locate the pollination group in the specifications table. From here, you can find a partner with either the same pollination group, the one above or below.