Hey there,
Allowing a form to be sent to an 'undetermined user' has some drawbacks that you should be aware of. When allowing the visitor to choose where the form is sent bypasses any spam security. If a spammer happens to stumble across a form like that, they can start sending spam emails from your site to anyone they want.
To combat this, we do allow you to choose who the form is emailed to, but that is a feature located in the admin, so you have to be verified to change the 'send to' address.
As for attaching a file, that's not necessarily what a form is for. All forms are sent through email, which is not considered a file sharing system. If you need to share files, we would suggest you contact us directly (service@gutensite.com) and have us create a solution for you.
I hope this has been useful.
Thanks,
Steven