The best place to do it would be a batch processing custom stage in the Advanced Workflow by adding it before or after the Export stage. On creating a new stage select Automatic type:



Since the whole batch is required at this stage, make sure that Wait for all documents of a batch option is enabled:


The type should be Batch processing:


This is just some sample script that demonstrates how to iterate through each document in a batch and get the values of the fields or document definition name matched on a document:

​​​for (int i = 0; i < Documents.Count; i++)
{
    //getting Document Definition Name matched on a document
    string docdefName = Documents[i].DocumentDefinition.Name;
 
    //checking first that the document has the field  
    if (Documents[i].HasField("Section name\\FieldName"))
    {
 
        string fieldText = Documents[i].Field("Section name\\FieldName").Text;
 
        //for debugging purposes you can use Processing messages/errors. They will be written in the task log in the Processing Server Monitor
        Processing.ReportMessage("fieldText: " + fieldText)

    }

}