If you have iManage Work and Microsoft 365 accounts and have read/write access or full access to a file saved to iManage Work, navigate to the file and open the file in edit mode using Microsoft Office for the web even if the file is marked with  against it. This makes you a co-author of the file as there are already other user(s) editing the file in Microsoft Office for the web. If you see a lock icon () against a file, you can then only view the file using Microsoft Office for the web. 

If you receive the URL from within the editing session in Microsoft Office for the web, you can select the URL and open the file directly in Microsoft Office for the web to make changes. You must have iManage Work and Microsoft O365 accounts and have read/write access or full access to the file. 

If you receive the file link sent to you by using the Copy Link option, selecting the file will open it in Preview, by default. Use the Edit using Microsoft Office for the web option to make your edits.