The Sales Orders feature is available in the Sales Pack extension.
A sales order is a document representing a confirmed customer order, and contains a group of products or services with their quantities and prices. Sales order is usually sent to a customer to confirm the sale before delivering the products and/or services the customer has ordered.
Sales orders contain the same information as a quote: line items (products or services), their prices, taxes, shipping details, etc. In fact, sales orders are quite similar to quotes, but they are a confirmation of the customer’s expressed desire to purchase. From the customer’s perspective, sales orders are useful as they reduce the possibility of human error, and indicate the exact delivery details of the ordered products and services. On the other hand, your employees can use sales orders to leverage internal inventory management, to know how many items are produced, delivered and remain in stock.
In EspoCRM, sales orders can be either generated from the related quote and opportunity records or created manually by employees. Invoices and delivery orders can subsequently be created from sales orders.
Sales orders can be printed to PDF. You can create multiple custom templates, which include your custom fields and fit your company design. The PDF can be send to the customer in email.

Documentation
For more detail information on using Sales Orders, see the documentation.