How can I generate a pdf from web URL with Symfony 4?

I try to generate a pdf from webURL with the snappy bundle:

class PagesController extends AbstractController
{
 /**
  * @Route("/pdf", name="pdf")
  */

  public function pdf(Request $request)
  {
    $snappy = $this->get("knp_snappy.pdf");
    $snappy->setOption("encoding","UTF-8");

    $filename = "mypdf";
    $webSiteURL = "http://www.stackoverflow.com";
    return new Response(
      $snappy->getOutput($webSiteURL),
      200,
      array(
        'Content-Type' => 'application/pdf',
        'Content-Disposition' => 'inline; filename="'.$filname.'.pdf"'
      )
    );
  }

But when I try to open the pdf I get the error message:

Service "knp_snappy.pdf" not found: even though it exists in the app's container, the container inside "App\Controller\PagesController" is a smaller service locator that only knows about the "doctrine", "form.factory", "http_kernel", "parameter_bag", "request_stack", "router", "security.authorization_checker", "security.csrf.token_manager", "security.token_storage", "serializer", "session" and "twig" services. Try using dependency injection instead

This is my config/packages/knp_snappy.yaml file:

knp_snappy:
    pdf:
        enabled:    true
        binary:     /usr/local/bin/wkhtmltopdf
        options:    []
    image:
        enabled:    true
        binary:     /usr/local/bin/wkhtmltoimage
        options:    []

One approach to solve this was, I tried to add use Knp\Component\Pager\PaginatorInterface; to my Controller, but then I get the error message:

Cannot determine controller argument for "App\Controller\PagesController::pdf()": the $paginator argument is type-hinted with the non-existent class or interface: "Knp\Component\Pager\PaginatorInterface".

Another approach to solve this was adding to my controller:

  public static function getSubscribedServices(): array
{
    $services = parent::getSubscribedServices();
    $services['fos_elastica.manager'] = RepositoryManagerInterface::class;
    $services['knp_paginator'] = PaginatorInterface::class;

    return $services;
}

But then I get the error message:

The service "App\Controller\PagesController" has a dependency on a non-existent service "App\Controller\RepositoryManagerInterface".

You can directly inject your dependencies into controller’s action like

use Knp\Snappy\Pdf;
class PagesController extends AbstractController
{
  /**
  * @Route("/pdf", name="pdf")
  */

  public function pdf(Request $request, Pdf $snappy)
  {
      $snappy->setOption("encoding","UTF-8");

      $filename = "mypdf";
      $webSiteURL = "http://www.stackoverflow.com";
      return new Response(
         $snappy->getOutput($webSiteURL),
      200,
      array(
         'Content-Type' => 'application/pdf',
         'Content-Disposition' => 'inline; filename="'.$filname.'.pdf"'
      )
    );
   } 

Make sure service autowiring enabled in service.yml file https://symfony.com/doc/current/service_container/autowiring.html#