Whenever you enter the 4 digit pin, remember to check the box "remember pin" and you won't have to enter it again.
You may also choose to save your voucher by adding the page to bookmarks, add to favourite.
I would suggest "add to homescreen" as it creates a shortcut in your mobile homescreen.
Click on it to access your voucher, even when you close the browser page accidentally, it will still redirect you to your voucher.