General:
* Revising
* Proofreading
* Correcting
* Amending
* Polishing
* Refining
* Improving
* Adjusting
* Enhancing
* Reconstructing
* Re-writing
More specific:
* For written text:
* Copyediting
* Line editing
* Developmental editing
* Substantive editing
* Fact-checking
* Copywriting
* For audio/video:
* Sound editing
* Video editing
* Post-production
* For images:
* Image editing
* Photo editing
* Retouching
More informal:
* Fixing
* Tweaking
* Cleaning up
* Touching up
* Making changes
The best synonym to use will depend on the specific situation and what you are trying to communicate.