I previously wrote an article describing the different Order settings of Salesforce OOTB. Once you have enabled those settings, some additional adjustments can still be made at either a profile or permission set level to allow users edit activated orders.
All of the below settings are in the App Permissions in the Sales section:
2. Activate Orders – this will be needed if the user will be setting the Order to Active – this is an important step in the ordering process, so any user involved should have this permission.
3. Create Reduction Orders – this is in conjunction with enabling reduction orders via the Order Settings. This allows a user to be able to take this action.
4. Delete Activated Contracts – this is a setting that very few people should have given the implications of deleting a Contract.
5. Edit Activated Orders – this setting is important if you have users that will need to modify something on the Order after it is activated; otherwise, they will get presented with a validation rule.