How to limit maximum quantity to 1 for one given product type ?
We sell PDFs online. Visitors can buy a printed / shippable version. In that case they must be able to select a quantity. But they can also choose to buy a downloadable version. In that case we want to enforce a maximum quantity of 1 for example if the visitors click several times on the add to cart button...
Printable / shippable is one product type, Downloadable is another one.
I am trying to use Rules to do that but for now haven't had any success...
How would you do it ?