Even though the RBP to generate document has been given you would observe "An application error" while trying to select any values from the drop down in "manage document template mapping"
SuccessFactors Employee Central Document Generation
Reproducing the Issue
In addition to the document generate RBP you would also need to provide configure business rules permissions as well to avoid getting this application error
Document generation Manage document template mapping Apllication error , KBA , LOD-SF-EC-DOC , Document Generation , Problem