Retail promotions - idoc download free goods

Hello,

Regarding promotions it seems the information can flow in several idoc's: WP_PLU, WBBDLD, WPDREB, and eventually others.

In the specific case of free goods promotions I cannot find this information in any of this idoc's.

(the example on WAK* is: for each 5 EAN sale you'll giveaway 1 EAN extra)

Any info on this?

Regards!