Dynamic file creation / manipulation for digital downloads

I original posted a similar question in Developers but seeing as it's not answered I've probably put it in the wrong area.

I'm after some clarification on being able to present a file for download that is customised for the user once purchase has been completed . I.E. watermarked eBook/PDF, mp3 (i.e. edit the ID3 to have the download date, receipt number or name in their).

Assuming what ever action I need done I can do via an outside script I just need a place to call this script with the user and file reference.

Is this possible with NOP? If so where would this occur?

Any help at all would be greatly appreciated.

Sorry previous post is here
https://www.nopcommerce.com/boards/topic.aspx?topicid=4302

I did mean to include it in the the first post.

so no one has ever wanted to do this? dynamically alter or watermark a file before download?

Anything is possible in nop - with development of course :)

You will need to hook into the order placement process (have a look in OrderManager) and check the items on the order to determine whether you need to create your custom download.