Some of your product can be downloadable. If so, go to Admin > Products >Products&Categories >(your product) > Edit > Downloadable/Software tab and fill out the following fields:

• Downloadable marks the product as downloadable.
• Download Period specifies how long the link will be active.
• Path to Downloadable File specifies the full product address. Note that the link will be encrypted automatically for the security purposes.
• Activation Options. You can also set the system to generate a random activation number (something like 1234-ABCD-EF12-DF12).You can choose not to generate serial number at all or you can select the serial number from the Predefined List field (which is below Activation Option Field).

Note: You can limit activations in the Activation Options by specifying the maximum number of activations.

• Predefined Serial Numbers allows you to set the serial number/s of a downloadable product. You can set any quantity of serial numbers.

In order to save the changes, please click the 'Update' button.