How to Check a Redaction Worked: Select, Search and Open in Another App

Published: Oct 19, 2026 | Updated: Oct 19, 2026 | About (Japanese)

Key points

Drag over the black area to select
Search for the words you hid
Open it in another app too

Even if you think you redacted something, you cannot tell from appearance alone whether it is really hidden. Before handing it over, check in three ways.

1. Drag over the black area to select

Drag with your finger or mouse over the black area.
If text is highlighted in blue, text remains underneath.
If nothing is selected, it is fine.

2. Search for the words you hid

Use the PDF viewer's search to look for the names or numbers you meant to hide.
If not found, it is fine.
If found, that page still has text.

3. Open it in another app too

Open it in another PDF app or in a browser, on a computer or phone.
Check that the black areas are still black in the same way.

If something remained

Start again in Black Out (Redact) Parts of a PDF from the original PDF.
Redacted pages become images, so the text underneath normally does not remain.
Check again in the three ways above.

Checking the coverage

Check that all of the text you wanted to hide is inside the black. If an edge sticks out, part of the text shows.
Drawing the box a little larger is safer.

Use "Black Out (Redact) Parts of a PDF" (free)

Tools that go well with this

Convert a PDF to Grayscale (Black & White): Turn a color PDF into grayscale or pure black and white, ready for monochrome printing, copying or fax. Choose the resolution.
Extract or Delete PDF Pages: Keep only the pages you need, or remove the pages you don't.
Compress PDF: Shrink a PDF to fit under a size you choose, for upload limits.

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