If you want to ensure you are always making secure file transfers from your core network, you can set up a protected channel. This way, rather than encrypting individual files, you simply send them through the protected channel that shields them from other traffic.
VPNs are the best known examples of this by allowing devices that have been set up with the correct authorisations to connect remotely to a closed network as if the device were physically part of the network.
However, while VPNs are able to reroute your IP address, they are not the most secure method of transferring data and should always be approached with caution. If a breach occurs during the use of a VPN, your communication may be open to monitoring and logging.