Delete Keynotes From An iPad
Open Keynote on your iPad and click on Presentations. Tap the one you want to delete and hold your finger until your presentations start to wiggle. Tap that presentation a second time and you will see a blue box around it.
Tap the trash can in the upper left corner and you will see the option to delete it. Just tap Delete Presentation and it will be gone (never to return). To delete several at once click on each one till the blue box appears and them tap the trash can.
Once you delete it, the other presentations will stop wiggling and your screen will return to the normal presentations view.
This is a good way to free up space on your Cloud.