Two permissions, which can be assigned ad hoc or through a Security Class, apply to versioning.
Version Documents permission
Version permission (in addition to the View permission) is required to view any prior version of a content item other than the current published one. It also allows metadata changes, content changes, and other operations on a draft and is subject to other, applicable permissions (such as Modify)
Version Publishing permission
Version Publishing permission is required to change what version of a document is published, either by Checking In a draft, Promoting an archive, or unpublishing the Published version.
In addition to these permissions, a draft may be owned by a specific user, thereby preventing any other users from modifying it.
Drafts may be owned, meaning they can only be modified by one user – the draft owner. A draft that is not owned may be viewed or modified to anyone with Version and other applicable permissions to that item’s security class.