Is there way of stopping a new workflow from being triggered when an Approver makes changes to a page submitted by an Editor? A second workflow is created when an Approver makes changes resulting in the first workflow becoming redundant.
From what you describe I guess your workflow definiton is triggered to start automatically when a page is saved.
If you change the definition so the workflow is started when a page is created instead of saved then a new workflow instance is not created when the page is updated. Another option is to not have the workflow definition configured to start automatically but instead that the editor starts it manually from workflow tab.