There is a Merge Stage in Parallel Jobs.

Here you can give one Master data  set (file) and any number of  updated data set (files). The output will be  merge of Master and updated data sets along with reject data set. The number of reject data sets are equal to the number of updated data sets.

The output data set will be all the columns from Master data set plus any additional columns from the updated data set. Here the key column values of master and update data sets must be same.