The Invoice Title – TAX INVOICE

Hi @johnhedouglas:

You can achieve this with a code snippet, as described in the documentation: Custom PDF filenames.

For your specific case, you can use this code snippet:

/**
 * PDF Invoices & Packing Slips for WooCommerce
 * Customize the PDF invoice title
 */
add_filter( 'wpo_wcpdf_invoice_title', function( $title, $document ) {
    $title="Tax Invoice";
    return $title;
}, 10, 2 );

If you haven’t worked with code snippets (actions/filters) or functions.php before, read this guide: How to use filters

Alternatively, with the Professional extension, you can do this directly from the plugin settings: