So things could be tougher in the UK. However, in the United States, there is only evidence that both parties have agreed on conditions. You can keep the physical contract… I have a copy. I just need written evidence that they saw it and accepted it. E-mail is usually sufficient. However, in most cases, I get a fax. There have been a few cases where I emailed an attached phone photo of the signed contract (as well with me). Without having to keep your promises, the customer may not feel ready to sign a contract and wait for your delivery ingredients. If you commit to additional tasks before you graduate, do your best to keep up with these efforts and speed up the sales process. Confidentiality agreements are a matter of trust.
If you are asked to sign an NDA when you enter into a new business relationship, this is likely because the person or company you work with does not have the ability to determine whether you are keeping your confidential information confidential. Asking them to sign a legally binding document is probably the only sure way to establish a culture of confidentiality.