For cPanel/WHM, to enable PDO in the system you can use EasyApache:

1. Login to WHM
2. Click Apache Update
3. Click Start Customizing Based on Profile
4. Select an Apache version
5. Click Next Step
6. Select PHP 5
7. Click Next Step
8. Select a version of PHP 5
9. Click Next Step
10. Click Exhaustive Options List button
11. Scroll down to the check box labeled PDO
12. Click Save and Build