My intent with the document I've created in Adobe Illustrator was to save one as an original and one as a copy with a few different characteristics. Accidentally, I saved both with the changed characteristics. How can I revert one back to the original?
The Revert function in Illustrator takes you back to your last Save.
If you saved over your working copy AND your back-up copy, then the only option is to find an older file that existed before you made the changes.
If you do regular back-ups or use backup software, you'll have to go back to that.
On the Mac if you have Time Machine running, you can go back and restore a previous version of the file.
If that's not an option, then you'll have to re-do the work.
If you've closed the file then you can't. Otherwise you can try to Undo (Ctrl+Z ) until it is at the point you want, then Save it how you originally intended to. There is no
History as there is in Photoshop, but the Undo is vastly more powerful than a single step-back.
You could also
Revert to get to your last save, again if you didn't close the file.
In either case you have to either work back to get to your Original, or Revert to the original and redo the changes you had wanted to save in the Copy.