How to show preview of entered values in previous steps in webform with multiple steps
You can try Webform Bonus Pack module, it have the option to preview webform fields before submission.


  which allows you to add a summary component directly to your form in
  the same way you would add a textfield or any other component type.
  Install that module and add a summary field to your form, selecting
  which fields you would like to include in the summary. If you would
  like it on its own page, make sure to add a pagebreak component first.


also take a look at this https://drupal.org/node/435232