Magento – Download Magento 2.0.2 with direct download link

I know this does not solve your problem, but maybe it makes you rework the functionality:

Actually the correct behaviour when accessing files directly from /media/downloadable/ should be a Permission denied.

Why?

Anyone could just do a directory traversal in your /media or /media/downloadable directory and download all the files in there automatically.

If you don't care about this fact: go ahead.

If you do: Try to find another solution to download the files.

You can use the Sample section/function of the downloadable products which is intended to be used to preview the files. Just upload your file there.

This is the sample code for download pdf in magento2

namespace Namespace\ModuleName\Controller\ControllerName;

use Magento\Framework\App\Filesystem\DirectoryList;
class Download extends \Magento\Framework\App\Action\Action
{
protected $directory_list;
protected $fileFactory;
public function __construct(
        \Magento\Framework\App\Action\Context $context, 
        DirectoryList $directory_list,
        \Magento\Framework\App\Response\Http\FileFactory $fileFactory) {
    $this->directory_list = $directory_list;
    $this->fileFactory = $fileFactory;
    parent::__construct($context);
}

public function execute()
{
    $file = $this->getRequest()->getParam('file');

    if(isset($file) && !empty($file)) {

        $pdf = \Zend_Pdf::load($this->directory_list->getPath(DirectoryList::MEDIA) . DIRECTORY_SEPARATOR . $file);
        $fileName = test.pdf;
        $this->fileFactory->create(
        $fileName,
        str_replace('/Annot /Subtype /Link', '/Annot /Subtype /Link /Border[0 0 0]', $pdf->render()),
        \Magento\Framework\App\Filesystem\DirectoryList::VAR_DIR,
        'application/pdf'
        );
    }
}
}