Text field on orders

Hello Everyone,

I want to add a greeting card with my product.
I have selection list and I am able to add it as a variant, but how can I add a greeting card to the parent product.

Thanks

What do you mean? Text field on orders?

?
As attachment in mails? As download?
$oParent = $oArticle->getParentArticle(); ?

To answer the question it would be great, to have a bit of code.