If you need more space around your imported Powerpoint's slides, try the following:
- Open a PowerPoint in Apple's free Keynote app.
- Tap "…" in the top right corner.
- Tap "Print".
- Tap the bottom left layout option.
- Tap "Next".
- Pinch to zoom in on the file's print preview.
- Tap the share button in the top right corner.
- Tap "Copy to Notability".