He's pardoned a number of people to the tune of various controversies, including the question "Can a president take back a pardon, once he's made it?" The answer may be yes, if the actual instrument hadn't been delivered.
There seems very little rhyme or reason to the pardons, but this is definitely an open-borders pardon. Agents Ramos and Compean, who were defending the border, will spend Christmas behind bars.
As for the rancher, we won't grudge him his restoration to full citizenship and voting rights, but current employers of illegals, who are fond of insisting that their crops will "rot in the fields" if they can't have cheap, illegal, labor, should read my post The Needs of America's Farmers.