How to perfume postcards?

We're making invitation postcards of the new pavilion "Invisible White" opening in July.

I would like to perfume the card.  Ideally with scratch & sniff, but it's very, very expensive.

So I thought of various methods of perfuming the postcards.

Normally card itself has a strong odour of paper and paint.  To fight against it is quite some work!!!  But it's not impossible.