Generate pdf file from pdf string and image string content in Magento 2.0

here we will learn, how to generate pdf file if you have string data of pdf and image.

public function generatePdf()
{
   $objectManager = \Magento\Framework\App\ObjectManager::getInstance();
   $labelGenerator = $objectManager->create('Magento\Shipping\Model\Shipping\LabelGenerator');
   $labelContent[] = base64_decode((string) $imageString); //you can add more image strings.
   $outputPdf = $labelGenerator->combineLabelsPdf($labelContent);

   $fileFactory = $objectManager->create('Magento\Framework\App\Response\Http\FileFactory');

   return $this->fileFactory->create(
         'Labels.pdf',
          $outputPdf->render(),
          \Magento\Framework\App\Filesystem\DirectoryList::VAR_DIR,
          'application/pdf'
       );
}

By calling this function you can generate pdf file from string content.