this should be easily possible. Just create the mappings in Midi Translator from the MIDI command to the keyboard shortcuts in Powerpoint to do what you want.
E.g. Pad 1 to PageDown:
Make sure the pad MIDI controller is connected to the computer and that it is selected as MIDI IN in the menu of MIDI Translator.
Start a new Translator Preset
Add A Translator
Click Edit Translator
As Incoming Action, choose MIDI
enable "Capture MIDI" and press the MIDI pad 1
select the MIDI message that stops with "00" (zero zero, not o o)
(do not use the message with "oo" or so)
As Outgoing Action, choose Keystroke
in the field, type in the key (combination) exactly as you'd
press it in Powerpoint
Press Apply. Now switch to Powerpoint and press the MIDI pad. It should turn the page down!
Let us know if that's working.