Two PCs that are both running on Ubuntu can share files in a number of ways. We use USB devices & swap them to synchronize files between two PCs in what was called a ‘sneaker network‘. One better way is to use an SSHFS or ‘Secure Shell File System’ network More here

SSHFS uses OpenSSH to provide secure communication between PC’s/With the network connected the local PC user will be able to transfer,open as well as edit files on the remote PC as if they were on his own machine. The remote files will look and act just like the files on the local PC