generating PDF file when submitting the form

I have following business scenario:
1. User fills out the form (webform module)
2. User clicks on button "Submit"
3. The PDF file is generated, (user can download it), and then user is redirected to page where he can see "thank you note" and info what to do with downloaded PDF.

I would like to call PDF generation method when the form is submitted, so that user that fills out the form can get the PDF (and not only admin).

I tried to look at the code, but since my PHP experience is very limited I would need some help from you.

I have found two functions in webform2pdf, which, I believe, are responsible for generating PDF:
- webform2pdf_download_pdf_form(&$form_state, $node)
- webform2pdf_download_pdf_form_submit($form, &$form_state)

As far as I understand I should call one of them when user clicks SUBMIT button on the form. I would go with the first one, as second one is probably for generating PDF from multiple records.

Having this I identified function in webform module, in webform.module file, called:
- webform_client_form_submit($form, &$form_state)
which, I belive, is called after user clicks SUBMIT button. It looks like this (just last two statements):

if (isset($form_state['values']['submission'])) {
    drupal_set_message(t('Submission updated.'));
    $redirect = NULL;
  }
  elseif (valid_url(trim($node->webform['confirmation']), TRUE)) {
    $redirect = trim($node->webform['confirmation']);
  }
  // Check if the form should redirect to an internal URL, strip tags off
  // first in case a WYSIWYG editor messed it up.
  elseif (preg_match('/^internal:/', trim(strip_tags($node->webform['confirmation'])))) {
    $path = preg_replace('/^internal:/', '', trim(strip_tags($node->webform['confirmation'])));
    $redirect = array(trim($path), 'sid='. $sid);
  }
  elseif (preg_match('/^message:/', $node->webform['confirmation'])) {
    $message = preg_replace('/^message:/', '', $node->webform['confirmation']);
    drupal_set_message($message);
    $redirect = NULL;
  }
  else {
    $redirect = array('node/'. $node->nid .'/done', 'sid='. $sid);
  }
  $form_state['redirect'] = $redirect;

Hence I should add the webford2pdf function invocation somewhere at the end of webform_client_form_submit function, probably just before $form_state['redirect'] = $redirect; . (Please correct me if I'm wrong...)

The question is, assuming my thinking until now is correct, what parameters should be passed to webform2pdf_download_pdf_form function in order to generate PDF?

Hope some could help me in this. Please let me know if I can provide any more information.

Thanks!
Damian