This has to be completed on each individual person and cannot be done in bulk.
Use the following steps to delete personal information from a persons skill documents.
Navigate to Person on the sidebar
Select desired employee
Click the Skills tab
Select the Skill name
Click on the arrow to select the document
Click Purge (you will then get a message asking if you are sure - this is in place as this process cannot be undone)
Click Purge again
Once this is done, the document will be removed from the person's Traffio skills and will no longer appear in any historical data within the Traffio portal.