Download Instruction Manual on Linked Product - Order one product with attribute - pu

I have a product that fits multiple applications, but needs seperate instructions for those applications.

I have one copy of the product, linked to different categories. Each category is one instance of how it could be installed. From a drop down list (made from the attributes controller I assume) I would like the purchaser to select which instructions they would wish to have, and by doing so when that item is added to the cart, the instructions are also.

Example:

I have three categories: Red Shoes, Brown Shoes, and Green Shoes; and one product that fits all of them, black laces, but is installed in them differently. This product (black laces) I have linked to all of the categories (different colors of shoes).

When someone looks at the laces, I need for them to have a menu where they select the type of shoe they are intended for. When they are ordered, I need another item, a download of the correct instructions for that selection, to be included on the order also.

Would this be best to do without linking? If so, how would I force the other item to be entered?

Thank you for any help,

Peter
[email protected]