From the TOOLS menu, or Version Settings Actions menu, click lock this version to prevent changes to a specific version.
This is ideal when you are collaborating on a drawing, or want to compare versions without the risk of making accidental changes, and you are not ready to “publish”.
The TOOLS and Actions menus will automatically update to show that this version is now locked.
Copy it to a new version to make changes.
Or, click publish this version in the TOOLS menu if no more changes are required to publish it.