If you want to duplicate ADs (for example, for recurring inspections) you can easily do that by clicking on "Duplicate Multiple ADs" in the AD list header:
For example, certain Cessnas have a recurring inspections regarding exhaust system corrosion (AD 2000-01-16) which requires recurring inspections. To duplicate this AD (as per inspections and MOCs), simply check the box next to the AD you want to duplicate and then click Add to Duplicates List:
You'll get a warning making sure you want to duplicate the selected AD - hit Duplicate Checked ADs again to finish the process and you will see the AD duplicated.
Repeat as many times as required.