The changes to the print preview window are not under the control of Print Edit WE. When you click on the 'Preview' button on the Print Edit WE toolbar, this invokes Firefox's standard print preview feature, which has changed recently. You can confirm this by selecting 'File' > 'Print Preview' on Firefox's main menu bar, which will show the same preview as Print Edit WE.

You can show Firefox's old print preview by setting the "print.tab_modal.enabled" preference to "false" in the "about:config" Advanced Preferences.