Have there been any attempts to turn free-trade agreements into Pareto improvements?
The US has a  "Trade Adjustment Assistance" for (almost) this exact purpose. 


  Trade Adjustment Assistance (TAA) is a federal program of the United
  States government to act as a way to reduce the damaging impact of
  imports felt by certain sectors of the U.S. economy. The current
  structure features four components of Trade Adjustment Assistance: for
  workers, firms, farmers, and communities. ...it was proposed by President John F. Kennedy as part of the total package to open up free trade. President Kennedy said: "When considerations of national policy make it desirable to avoid higher tariffs, those injured by that competition should not be required to bear the full brunt of the impact. Rather, the burden of economic adjustment should be borne in part by the Federal Government."...As a 2012 Report by the Joint Economic Committee states: "TAA needs to remain an integral part of trade policy because it compensates those harmed by import competition without sacrificing the larger demonstrable benefits of trade


Trade Adjustment Assistance at Wikipedia 

Canada had a program like this into the 1980's. The comparable EU program is called The European Globalisation Adjustment Fund.