One of the best features of Google Drive is the ability to share and modify files with other users. Today, Google's building up on its permission system, allowing owners of shared files to lock certain functions like downloading, printing, or copying.
Previously, if you shared a view-only file, Google would allow users to make a copy, download it locally, or print it out. While that wouldn't affect your existing file, you may not want to allow just anyone to make a copy. Now, you can lock it so these options aren't available. Additionally, if you add other editors to a file, you can now prevent them from adding other people without your knowledge.