Currently snapshot docs contains the cp command details for copying the snapshot files to regular dfs tree.
Copying a file from snapshot s0:
hdfs dfs -cp /foo/.snapshot/s0/bar /tmp
Since there are important properties(acls, xattrs..etc) for a file may need to copy back. But looking at this doc may mislead to copy with out using any options. So, It may be worth mentioning aboit that properties. Infact it should copy all properties by default from snapshot file.