The Prestashop delivery slip includes a unique prefix and and number that can be adjusted in the backoffice interface.  The following tutorial will show how to modify the delivery slip options in PrestaShop 1.5

Changing the Delivery Slip options in PrestaShop 1.5

1. Log-in to the Prestashop administrator dashboard as an Administrator
2. Hover the menu bar where it says ORDERS, scroll down and click on DELIVERY SLIPS.  You will see the following screen:

   

   
   If you have the Multishop option activated, you may need to select the shop that you wish to see in order to narrow down the list of delivery slips you will generate.
   
   Note that the check boxes will not appear unless you select a specific shop.  If you select ALL SHOPS, the options will pertain to all of the shops being managed by your installation.

   Scroll down to the section labeled DELIVERY SLIP OPTIONS

3. If necessary click on the check box to activate the DELIVERY PREFIX.  Note that there will be a different DELVIERY PREFIX for each language installed and active in Prestashop.  Type in the prefix you wish to use.  Keep it simple and short.
4. Click on the checkbox to activate the DELIVERY NUMBER.  This number will be the starting number for the next delivery slip printed.  The number increments sequentially from whatever number you select as the starting number.
5. Select SAVE in order save our entries.

If you are dealing with international destinations, or if you need to make your delivery slips unique, then you should modify the delivery prefix and number.  This is especially import when you are managing multiple stores with PrestaShop 1.5.  Here's an example of the invoice entries set by the delivery number and prefix: