Download instructions only on downloadable products

We wish to have a store where some products are downloadable, but some are physical products.

To try to explain how the download system works, we want to have the download instructions only on the product pages of the downloadable products, not on the product pages of the physical products.

I don't mind if this is automatically added, or via a tick box in admin.

Does anyone know of a way we can achieve this?

Thanks

Version -- in use or contemplated? As a matter of course, OC does not add any download instructions, those must be added manually. If for a set of downloadable products, whether gathered together in a cohesive single category or strewn among physical products in otherwise normal caregories, you can add downloading instructions into descriptions -- once for category of downloadable products, or once each in product descriptions.