Encryption / data protection

We are looking at solutions for data protection. We have multiple network shares that contains data that is  very important to the company. This data does need to be seen and edited by the workers. What we want is a solution where they can access it and edit it on their local pc, but cannot make copies of it. For example if a employee leaves, we do not want them to be able to take a copy of the information.  Is there software out there that does this sort of thing, where the end user needs to be running a client to be able to decrypt the data?