Open Make PDF smaller from the Home screen (or use its own page link).
Tap Choose files and select all the files you need (you can select several at once).
Forgot a file? Tap Add more files. To remove one, tap ✕ next to it.
Choose 500 KB.
Tap the big purple Start button and wait a few seconds.
When you see Done!, tap Download. The new file is saved on your phone or computer.