I have been looking for a cart I can intergrate into my website to to sell digital downloads. I am only after selling one item. My issue is this,
Say I have 100 pdf's uploaded to a download folder, but I only want to sell each pdf once.
For the buyer, all 100 pdf's look and are the same so I only need the one item listed on my web page.

So what I need is to be able to list one item, but each time the "Buy Now" button is clicked the next pdf is sent to them.

I don't want to list 100 items that all look the same.

Additiobal Option
The other trick if possible is to provide an option to allow the buyer to select the quantity if they want more than 1, if they select say 3, then the next 3 pdf's become downloadable to them.

I have googled for a cart that could do this and think Zen is my best bet, but can't find an answer to this on the site.

If someone could point me in the right direction I would very much appreciate it

I haven't setup zencart yet, I am hoping to find if zen can do this for me first.

Thanks