what is the General Idea to download a file after fill up the wp contact form?

In my WordPress website I am using Contact Form 7 plugin to show a form to get information from the users.

Now, I want user must be fill up the form and after that they can download a file. Only after fill up the form a file link will be show to download.

so I want to know what is your idea to get it done in WordPress ?

I searched google and found 3 plugins to do the job but is there any other custom way in WordPress ?

Thank You.

via Chebli Mohamed