Magento – How to we add header and footer to invoice pdf

magento\app\code\Namespace\Rewrite\etc\di.xml

<?xml version="1.0"?><config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
<preference for="Magento\Sales\Model\Order\Pdf\Invoice" type="Namespace\Rewrite\Magento\Sales\Model\Order\Pdf\Invoice"/>

\magento\app\code\Namespace\Rewrite\etc\module.xml

<?xml version="1.0"?><config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
<module name="Namespace_Rewrite" setup_version="2.0.1">
</module>

magento\app\code\Namespace\Rewrite\Magento\Sales\Model\Order\Pdf\Invoice.php

    <?php
namespace Namespace\Rewrite\Magento\Sales\Model\Order\Pdf;

use Magento\Framework\View\LayoutInterface;

use Magento\Sales\Model\Order\Pdf\Config;

use Magento\Sales\Model\Order\Pdf\Invoice as BaseInvoice;


class Invoice extends BaseInvoice
{

    protected $_layout;

    /**
     * Invoice constructor.
     * @param \Magento\Payment\Helper\Data $paymentData
     * @param \Magento\Framework\Stdlib\StringUtils $string
     * @param \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
     * @param \Magento\Framework\Filesystem $filesystem
     * @param Config $pdfConfig
     * @param \Magento\Sales\Model\Order\Pdf\Total\Factory $pdfTotalFactory
     * @param \Magento\Sales\Model\Order\Pdf\ItemsFactory $pdfItemsFactory
     * @param \Magento\Framework\Stdlib\DateTime\TimezoneInterface $localeDate
     * @param \Magento\Framework\Translate\Inline\StateInterface $inlineTranslation
     * @param \Magento\Sales\Model\Order\Address\Renderer $addressRenderer
     * @param \Magento\Store\Model\StoreManagerInterface $storeManager
     * @param \Magento\Framework\Locale\ResolverInterface $localeResolver
     * @param LayoutInterface $layout
     * @param array $data
     */
    public function __construct(\Magento\Payment\Helper\Data $paymentData,
                                \Magento\Framework\Stdlib\StringUtils $string,
                                \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
                                \Magento\Framework\Filesystem $filesystem,
                                Config $pdfConfig,
                                \Magento\Sales\Model\Order\Pdf\Total\Factory $pdfTotalFactory,
                                \Magento\Sales\Model\Order\Pdf\ItemsFactory $pdfItemsFactory,
                                \Magento\Framework\Stdlib\DateTime\TimezoneInterface $localeDate,
                                \Magento\Framework\Translate\Inline\StateInterface $inlineTranslation,
                                \Magento\Sales\Model\Order\Address\Renderer $addressRenderer,
                                \Magento\Store\Model\StoreManagerInterface $storeManager,
                                \Magento\Framework\Locale\ResolverInterface $localeResolver,
                                LayoutInterface $layout,
                                array $data = [])
    {
        $this->_layout = $layout;
        parent::__construct($paymentData,
            $string,
            $scopeConfig,
            $filesystem,
            $pdfConfig,
            $pdfTotalFactory,
            $pdfItemsFactory,
            $localeDate,
            $inlineTranslation,
            $addressRenderer,
            $storeManager,
            $localeResolver,
            $data);
    }

    /**
     * @param \Zend_Pdf_Page $object
     * @param int $size
     * @return \Zend_Pdf_Resource_Font
     * @throws \Zend_Pdf_Exception
     */
    protected function _setFontRegular($object, $size = 12)
    {
        $font = \Zend_Pdf_Font::fontWithPath(
            $this->_rootDirectory->getAbsolutePath('app/code/Namespace/Rewrite/Magento/Sales/web/fonts/arial.ttf')
        );
        $object->setFont($font, $size);
        return $font;
    }

    /**
     * @param \Zend_Pdf_Page $object
     * @param int $size
     * @return \Zend_Pdf_Resource_Font
     * @throws \Zend_Pdf_Exception
     */
    protected function _setFontBold($object, $size = 12)
    {
        $font = \Zend_Pdf_Font::fontWithPath(
            $this->_rootDirectory->getAbsolutePath('app/code/Namespace/Rewrite/Magento/Sales/web/fonts/arialbd.ttf')
        );
        $object->setFont($font, $size);
        return $font;
    }

    /**
     * @param \Zend_Pdf_Page $object
     * @param int $size
     * @return \Zend_Pdf_Resource_Font
     * @throws \Zend_Pdf_Exception
     */
    protected function _setFontItalic($object, $size = 12)
    {
        $font = \Zend_Pdf_Font::fontWithPath(
            $this->_rootDirectory->getAbsolutePath('app/code/Namespace/Rewrite/Magento/Sales/web/fonts/ariali.ttf')
        );
        $object->setFont($font, $size);
        return $font;
    }

    /**
     * @param array $invoices
     * @return \Zend_Pdf
     * @throws \Zend_Pdf_Exception
     */
    public function getPdf($invoices = [])
    {
        $this->_beforeGetPdf();
        $this->_initRenderer('invoice');

        $pdf = new \Zend_Pdf();
        $this->_setPdf($pdf);
        $style = new \Zend_Pdf_Style();
        $this->_setFontBold($style, 10);

        foreach ($invoices as $invoice) {
            if ($invoice->getStoreId()) {
                $this->_localeResolver->emulate($invoice->getStoreId());
                $this->_storeManager->setCurrentStore($invoice->getStoreId());
            }
            $page = $this->newPage();
            $order = $invoice->getOrder();
            /* Add image */
            $this->insertLogo($page, $invoice->getStore());
            /* Add header text */
            $this->drawHeaderText($page);
            /* Add address */
            $this->insertAddress($page, $invoice->getStore());
            /* Add head */
            $this->insertOrder(
                $page,
                $order,
                $this->_scopeConfig->isSetFlag(
                    self::XML_PATH_SALES_PDF_INVOICE_PUT_ORDER_ID,
                    \Magento\Store\Model\ScopeInterface::SCOPE_STORE,
                    $order->getStoreId()
                )
            );
            /* Add document text and number */
            $this->insertDocumentNumber($page, __('Invoice # ') . $invoice->getIncrementId());
            /* Add table */
            $this->_drawHeader($page);
            /* Add body */
            foreach ($invoice->getAllItems() as $item) {
                if ($item->getOrderItem()->getParentItem()) {
                    continue;
                }
                /* Draw item */
                $this->_drawItem($item, $page, $order);
                $page = end($pdf->pages);
            }
            /* Add totals */
            $this->insertTotals($page, $invoice);
            if ($invoice->getStoreId()) {
                $this->_localeResolver->revert();
            }
            /* Add footer content */
            $this->drawFooter($page);
        }
        $this->_afterGetPdf();
        return $pdf;
    }

    /**
     * @param \Zend_Pdf_Page $page
     * @param String $value
     */
    public function drawFooter(\Zend_Pdf_Page $page)
    {
        try {
            $font = $this->_setFontRegular($page, 10);
            $this->y -= 10;
            $value = $this->getFooterContent();
            $line = 52;
            if ($value !== '') {
                $value = preg_replace('/<br[^>]*>/i', "\n", $value);
                $page->setFillColor(new \Zend_Pdf_Color_RGB(0, 0, 0));
                $page->setLineColor(new \Zend_Pdf_Color_GrayScale(0.5));
                foreach(explode("\n", $value) as $textLine){
                    $feed = $this->getAlignCenter($textLine, 30, 520, $font, 10);
                    $page->drawText(strip_tags($textLine), $feed, $line, 'UTF-8');
                    $line -=16;
                }
                $page->setFillColor(new \Zend_Pdf_Color_GrayScale(0));
            }
            $this->y -= 20;
        } catch (\Exception $e) {
            $this->_logger->critical($e);
        }

    }

    /**
     * @param \Zend_Pdf_Page $page
     */

    public function drawHeaderText(\Zend_Pdf_Page $page)
    {
        try {
            $this->_setFontRegular($page, 16);
            $page->drawText('CUSTOMER INVOICE', 410, 800, 'UTF-8');
        }
        catch (\Exception $e) {
            $this->_logger->critical($e);
        }
    }

    /**
     * @return mixed
     */
    public function getFooterContent()
    {
        if($footerCms = $this->_layout->createBlock('Magento\Cms\Block\Block')->setBlockId('pdf_invoice_text'))
        {
            return $footerCms->toHtml();
        }
    }
}

magento\app\code\Namespace\Rewrite\registration.php

    <?php
    \Magento\Framework\Component\ComponentRegistrar::register(
\Magento\Framework\Component\ComponentRegistrar::MODULE,
'Namespace_Rewrite',
__DIR__
);