Magento2: How to get invoice pdf as response through magento rest api?

Question

I want to get the pdf invoice as response using magento rest api for mobile application. I got the invoice order history data

My code:

public function printInvoicePdf(Request $request)
  {
    echo "testing";

    $validator = Validator::make($request->all(), [ 
        'invoice_id'  => 'required'
        //'token' => 'required'
    ]);
    if($validator->fails()) 
    { 
      return response()->json(['error'=>$validator->errors()], 401);            
    }

    else 
    {

    $invoice_id=$request->invoice_id;
    //print_r($order_id);
    $get_admin_token=$this->authenticateMageAPI();
    //$apiURL=$this->API_URL."invoices/".$invoice_id."/pdf/".templateId."";
    $apiURL=$this->API_URL."invoices/".$invoice_id; 

    //echo 
    $headers = array("Authorization: Bearer ".$get_admin_token,'Content-Type: application/pdf');

    $ch = curl_init($apiURL);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET");
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

    // curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    //     "Authorization: Bearer ".$token
    // ));
    $result = curl_exec($ch);
    $response_get = json_decode($result);
    if(isset($response_get->message))
      {
        echo "testing3";
        $respose    = array("error_code" => 1,"data"=>$response_get); 
        $data_enode = json_encode($respose);
        echo  $data_enode;  
      }
      else
        {

          echo "testing2";
            $respose    = array("error_code" => 0,"data"=>$response_get); 
            $data_enode = json_encode($respose);
            echo  $data_enode;  
        }    
    }
  }

Any help would be appreciated