Try creating same methods which you want to override from AbstractPdf.php in your overided Invoice.php file. For example:

1) Create a preference for Invoice.php in di.xml

>`<preference for="Magento\Sales\Model\Order\Pdf\Invoice" type="Vendor\Module\Model\Order\Pdf\Invoice" /> `<preference for="Magento\Sales\Model\Order\Pdf\Invoice" type="Vendor\Module\Model\Order\Pdf\Invoice" /> 

2) In Vendor\Module\Model\Order\Pdf\Invoice, in you case create a method insertOrder

    /**
     * Insert order to pdf page
     *
     * @param \Zend_Pdf_Page &$page
     * @param \Magento\Sales\Model\Order $obj
     * @param bool $putOrderId
     * @return void
     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
     * @SuppressWarnings(PHPMD.NPathComplexity)
     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
     */
    protected function insertOrder(&$page, $obj, $putOrderId = true)
    {
        // comment relevent code according to your requirement
    }