exception needed for view only permission opening copy of PO in edit mode with custom button

I had to create a custom approval process for making changes to purchase orders. I have a user event script that adds a custom button to purchase orders. This button triggers a client script that uses the nlapiResolveURL() function to open a copy of the purchase order in edit mode. That way the user can make changes to the purchase order and save it, which then triggers a workflow with the approval process.

My issue is that the users that will be using this button should not have edit access to purchase order records. They have view access only. So, they are able to open this copy but any changes they make they will be unable to submit. I know that I could give them edit access and hide the edit button but they will still be able to see an edit button in the list view of purchase order records. I imagine I could hide that from them as well somehow but it seems risky to give them edit access at all.