Это - часть

 <a href="{{route('download',$details->report_id)}}" type="button" class="btn btn-primary download" data-report_id="{{$details->report_id}}" >Download</a>

HTML, Это - Маршрут:

Route::get('/download/{id}', 'users\UserController@getDownload')->name('download')->middleware('auth');

Это - функция:

public function getDownload(Request $request,$id)
{
                $file= public_path(). "/pdf/";  //path of your directory
                $headers = array(
                    'Content-Type: application/pdf',
                );
                 return Response::download($file.$pdfName, 'filename.pdf', $headers);      
}