bsk_pdfm_filter_date_filter_text_month
Default option null text for month dropdown is Month, you may use this filter to update it.
Example
/** * Change the default option null text of month dropdown in date filter * @return new option null text */ add_filter( "bsk_pdfm_filter_date_filter_text_month", "change_date_filter_month_text" ); function change_date_filter_month_text() { return 'Reset Month to filter PDFs'; }