I don't know if the NFL does this, but I know the NBA does. Basically teams can trade picks where if they fall between say #2 and #5, the team trading the pick will get to keep it, but will need to trade the following years pick. Basically conditionals attached to picks.
Example:
if 2017 1st round pick falls in the top 10,
trade 2018 1st round pick
else:
trade 2017 1st round pick