Functions I used in the donations setup referenced here: https://laurena.blog/collecting-donations-with-woocommerce/

functions-additions.php

/**
 * Function to remove the variable subscription price string
 * Add this to your child theme's functions.php file.
 */
function wc_remove_var_subscriptions_price() {
	return '';
}
add_filter( 'woocommerce_variable_subscription_price_html', 'wc_remove_var_subscriptions_price' );


function wc_subscriptions_custom_price_string( $pricestring ) {
    $newprice = str_replace( 'for 1 day', 'once', $pricestring );
    return $newprice;
}
add_filter( 'woocommerce_subscriptions_product_price_string', 'wc_subscriptions_custom_price_string' );


function lr_subscriptions_custom_price_string( $pricestring ) {
    $newprice = str_replace( 'every day once', 'once', $pricestring );
    return $newprice;
}
add_filter( 'woocommerce_subscriptions_product_price_string', 'lr_subscriptions_custom_price_string' );

/**
* // Custom redirect for users after clicking 'return to shop'
**/
add_filter('woocommerce_return_to_shop_redirect', 'lr_wc_return_to_shop_redirect');
function lr_wc_return_to_shop_redirect( $redirect ) {
     $redirect = '/products/donation/';
     return $redirect;
}

add_filter( 'pdf_template_order_total', 'lr_get_pdf_order_total', 10, 2);
function lr_get_pdf_order_total( $output, $order_id ){
     global $woocommerce;
     $woocommerce_pdf_invoice_options = get_option( 'woocommerce_pdf_invoice_settings' );

     if (!$order_id) return; 
     $order = new WC_Order( $order_id );

     // Check WC version - changes for WC 3.0.0
     $pre_wc_30    = version_compare( WC_VERSION, '3.0', '<' );
     $order_total = $pre_wc_30 ? woocommerce_price( $order->order_total ) : wc_price( $order->get_total() );
     $output =   __('', 'woocommerce-pdf-invoice') . $order_total;
     return $output;
}