I am running version 1.37.

Overview:
I sell files of text that a person can either purchase as a PDF, or as a Hardcopy. Shipping is free for PDFs, and hardcopy shipping is based on country. So I have cloned the shipping "Per Item" for a total of 3 (USA, Cananda, all other places outside USA AND Canada). So, at checkout, they have 2 options to choose from 1) PDF which is free shipping 2) Hardcopy, where price per item is showed based on their country.

Problem:
Based on the overview above alone, this works perfectly, except I would have to manually send out the files for those who choose PDF.

It seems the only way to get an automatic download is to put an attribute of either type radio or drop down, or checkbox. Most of the time my customers purchase 2+ items, and I think it would be a pain on each "adding to cart" page to have to manually select PDF. Also, if they forget to select this option, they will not be taken to the download.

What I would like:
-I would like for each item to be added to cart, then at the checkout page, they select either PDF or Hardcopy. Then after payment, if they selected PDF, they are automatically taken to the download page.

or

- Regardless if they choose hardcopy or PDF delivery, they are automatically taken to the download page after checkout.

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Is the only way to achieve an automatic download --> the user having to manually select an attribute option at every single add to cart page? Or is there a way where they can just select the radio option of PDF at the checkout page only and then be taken to the downloads?

I may be missing something quite simple... the Zen cart has been quite a learning curve for me, but so far I have implemented everything that I need and figured many things out, except for this- I am stumped!

Thank you in advance!!