If you're facing this error while trying to download a file from your server, it's most probably the SSL certificate that has been hosted on your server isn't correctly verified or maybe, you're using OpenSSL on a server running PHP 5.6.

As per the documentation, there are some changes that can be made to resolve it, like the following method:

<?php
public function foo(Request $request) {
    $arrContextOptions = array(
        "ssl" => array(
            "verify_peer" => false,
            "verify_peer_name" => false,
        ),
    );
    return Response::make(file_get_contents(asset('pdf/file.pdf'), false, stream_context_create($arrContextOptions)), 200, [
        'Content-Type' => 'application/pdf',
        'Content-Disposition' => 'inline; filename="file.pdf"',
    ]);
}
?>

Although, I won't recommend this unless you are testing it on a localhost environment as it's not secure and could have significant security implications because disabling verification can permit a Man in the Middle attack to take place.

Use it at your own risk!