Hi Sorin
I had the same problem yesterday as well. It would be great if someone can respond back, but AFAIK, you can only email files which were uploaded by the person filling out the Contact Form.
This is how I got around the problem for the time being
1. Upload the file you want to send via email to your website, with a publically accessible URL.
2. Password protect the file if you feel the need to.
3. In Contact Form 7, use the Mail(2) option to setup an autoresponder email.
4. Put the link of the file in the email. The autoresponder also gives you an opportunity to sell/provide actions to contact you.
Cheers.