Magento2 Invoice PDF issue

Question

I have added extra data to be display before subtotal in INvoice PDF but not display properly

Following is my code I added

foreach ($invoice->getAllItems() as $item) {
                if ($item->getOrderItem()->getParentItem()) {
                    continue;
                }
                /* Draw item */
                $this->_drawItem($item, $page, $order);
                $page->setLineColor(new \Zend_Pdf_Color_GrayScale(0.5));
                $page->setLineWidth(0.5);
                $page->drawLine(25, $this->y+12.5, 570, $this->y+12.5);
                $page = end($pdf->pages);
            }
            $this->insertText($page,$order->getGiftMessageId());
            /* Add totals */
            $this->insertTotals($page, $invoice);
            if ($invoice->getStoreId()) {
                $this->_localeResolver->revert();
            }

Where $this->insertText($page,$order->getGiftMessageId()); is my custom function

Also, following is the data for this function

public function insertText($page,$giftid)
    {
         $page->drawLine(25, $this->y, 570, $this->y); 
         $this->y -= 25;
         $lines = [];
         $_giftMessage = $helper = \Magento\Framework\App\ObjectManager::getInstance()->get('Magento\GiftMessage\Helper\Message')->getGiftMessage($giftid);
         if (!empty($_giftMessage->getSender())) {
            $page->drawText('Gift Message for this Order 2', 35, $this->y, 'UTF-8');
            $page->drawText('From:', 35, $this->y-26, 'UTF-8');
            $page->drawText($_giftMessage->getSender(), 65, $this->y-40, 'UTF-8');
            $page->drawText('To:', 35, $this->y-50, 'UTF-8');
            $page->drawText($_giftMessage->getRecipient(), 65, $this->y-60, 'UTF-8');
            $page->drawText('Message:', 35, $this->y-75, 'UTF-8');
            $page->drawText($_giftMessage->getMessage(), 65, $this->y-90, 'UTF-8');
            }
    }
}

The custom data gets hidden