There are two types of certificates, single and complete.
Single certificates (per module)
Single certificates for each module can be generated by a manager, but not by drivers.
Go to Reports > Build Report (or Search) > View a driver > Test results
Click on Certificate next to the result you want to create the certificate for.
Complete course certificates
Go to Reports > Drivers and courses > Manage drivers.
The certificate button will appear green and will be activated if the driver has completed all modules.
This creates a certificate that contains the best result from every module that the driver has registered a score for. For example, if a driver has taken the Emergencies module twice, scoring 88% and 100%, the certificate will only show it once with a score of 100%.
There may be other documents available such as the course validation statement or ID card, depending on the course.