Stat > DOE > Modify Design > Fold design > Specify

Fold the design to increase the resolution. You can fold factorial designs, Plackett-Burman designs, and split-plot designs. For more information, go to What is folding?.

Fold on all factors
Fold on all factors to increase the overall resolution of the design. If you fold on all factors, any term in the defining relation with an odd number of letters is eliminated.
Fold just on factor
Fold on a single factor to increase the resolution for a single factor. This type of fold is more common after a screening design, where many potential interactions are between unimportant factors. If you fold on a single factor, any term in the defining relation with that factor is eliminated.

In some cases, folding simply adds a replicate, and does not increase the resolution of the design.