Automated pdf version of the node that´s generated while the node is being created, and it´s automatically attached to that node

Hi there!
I´ve got this nodetype that after you generate it, you have a "download pdf version" link. This node has some complex information in it, and as that information can change over time, I need to be able to save and attach an automated pdf version of that very node in the moment that I´m creating the node.

I don´t know how can I do that. I´ve tried with Rules, but with no luck. Any thoughts on how to achieve this?

Thanks for your help and guidance!
Rosamunda