I get asked this question a lot, as many customers who are first time importers are concerned with having their product design stolen.
We are happy to sign a non-disclosure agreement with all of our customers. You would either have one drawn up yourself, or ask an attorney to put one together.
Afterwards, we can have our partner company in China sign the NDA too. We can also ask the factory to sign an exclusive contract with the PO where they agree not to sell your product to any other company but yours.