Integration is initially turned on by selecting the 'ProjectWise Integration' option for your version of Office through the ProjectWise Explorer installer.

The standard way to turn off integration is to uninstall ProjectWise Explorer, and then reinstall ProjectWise Explorer with Office integration turned off.

Once integration is installed, you can also turn it off and on as needed from inside the application through the COM Add-ins dialog (File > Options > Add-Ins > Manage COM Add-ins). Use this method to turn integration back on, if for some reason the integration gets turned off during your session.