Sorting is controlled by the PivotEngine, but it can be done through the PivotGrid also. You can sort a field by clicking on the PivotGrid's column headers.
The PivotEngine automatically sorts dimension (row and column) fields when it generates data summaries, but it does not sort measure (value) fields by default.
You can change the sort direction on dimension fields by setting the field's sort property in code.
Users may switch the sort direction by clicking the headers on any PivotGrid control attached to the engine (as long as the grid's allowSorting property is set to true).
The PivotGrid control does not show dimension field sort setting by default, but you can set the showRowFieldSort property to true if you want that feature.
Measure fields are not sorted by default. You can set their sort direction by changing the sortDescriptions property of the engine's pivotView collection (which contains the summary generated by the engine).
For implementation, refer to the PivotEngine Sort demo.