Open Hide private info from the Home screen (or use its own page link).
Tap Choose file and select your PDF from the phone or computer.
Tick what to hide: CNIC / ID number, Phone numbers, Email, Card numbers. You can also type Other words (separated by commas), like a name.
Tap the big purple Start button and wait a few seconds.
Open the downloaded file and check every page before you share it. Hidden text is removed, not just covered with a black box.