What happens to pages I do not mark?

Pages with no zones are copied as-is, so their text remains selectable. That is intentional when only one page has the sensitive line. It is also the way a missed page leaks. At least one zone is required for the redaction. After you download stem_redacted.pdf, walk every page you meant to cover.

Does this run in the browser?

Yes. Redaction is local for files up to 100 MB. The browser needs OffscreenCanvas so the marked page can be drawn and embedded. Draw the rectangles, export the file named with _redacted, and confirm the black boxes sit on the right lines. The original file on your disk stays put until you replace it yourself.

How many boxes do I need?

At least one zone is required. Beyond that, draw a rectangle for every stretch of text that must disappear, on every page where it appears. A single box on page one leaves the same number untouched on page four, because that page had no zone and is copied through. Err toward covering the whole line.

What should I check before I send the file?

Open stem_redacted.pdf and look at each marked page as a picture. Try to highlight where the words used to be. The covered text should be gone on those pages. Then check unmarked pages, because they still contain their original text. If a line survived, add a zone and export again. The work stays in the browser.

Why does the browser matter?

The flatten step needs OffscreenCanvas. A browser without it stops before the marked page can become a picture. Use a current Chrome, Edge, Firefox, or Safari build, keep the file at or under 100 MB, and draw the rectangles there. The black fill is #000, and the download name ends with _redacted.pdf.

Canonical Redact PDF Tool

Redact PDF: black out the words you marked

Q: Are the covered words still hidden in the PDF?

On pages where you drew a zone, the page is rendered to a canvas, the rectangles are filled black (#000), and that bitmap replaces the page. The underlying text on those pages is destroyed. Black out the words, then download a PDF where those marked pages are pictures. Proof the download by trying to select the covered line.

Black out the words, then download a PDF where those marked pages are pictures. Covered text on those pages is gone from the file.

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Written by Safaat Rahman Siham, Founder & Developer at Convertify4u. Contact us.

You need selected words gone from a PDF before you share it. Black out the words, then download a PDF where those marked pages are pictures. The work stays in the browser for files up to 100 MB. Draw rectangles over the text. Each page that has a zone is rendered to a canvas, the rectangles are filled black (#000), and that bitmap is embedded as the new PDF page. The underlying text on those pages is destroyed, because the page is now a picture. Pages with no zones are copied as they are. At least one zone is required. The browser needs OffscreenCanvas to build the marked pages. The download is named with _redacted before the extension. Proof it. Try to select the covered words and confirm they are gone on the pages you marked. A page you left without a rectangle still contains its original text.

Black rectangles that become part of the page

Marked pages are flattened to pictures with the black boxes baked in. Unmarked pages are copied through, so only draw where the text must disappear.

Draw the zones, at least one

You paint rectangles over the words that have to disappear. At least one zone is required before a download makes sense. Be generous with the box if a line is tight, and stay precise if a neighboring sentence must remain readable. The rectangles are filled black, #000, on the rendered page.

Marked pages become pictures

A page with zones is rendered to a canvas, the black rectangles are filled, and that bitmap is embedded as a new PDF page. The underlying text on those pages is destroyed. Black out the words, then download a PDF where those marked pages are pictures. Someone opening the file sees the black bars, and the covered characters are gone from the page content.

Unmarked pages stay as they were

Pages with no zones are copied as-is, text included. That is useful when only one page has the account number, and it is a mistake when you meant to cover a line and missed the page. The browser needs OffscreenCanvas. The file stays local, up to 100 MB, and the download is stem_redacted.pdf. Proof every marked page.

How it works

1
Open the PDF in the browser
Files up to 100 MB stay on the local path. The browser needs OffscreenCanvas for the marked pages. Use a current desktop browser if a phone tab struggles.
2
Draw a black rectangle on each secret
Cover every line that must disappear. At least one zone is required. Pages you leave bare are copied with their text still in the file.
3
Download and proof the pictures
The marked pages are pictures with #000 boxes baked in. The file is stem_redacted.pdf. Try to select the covered words and confirm they are gone.

Use cases

An account number on one page of a statement

Draw the rectangle there. That page becomes a picture, and the other pages can stay as they were if they have no secrets.

A contract with a personal address

Cover the address lines. Black out the words, then download a PDF where those marked pages are pictures.

A shared exhibit with a private email

Box the address, export stem_redacted.pdf, and proof that the text under the box is gone.

Problems we solve

A page you forgot still has selectable text

Pages with no zones are copied as-is. Go back and draw a rectangle on every page that needs it.

The browser stops before the flatten

Marked pages need OffscreenCanvas. Open the tool in a current browser that provides it, then draw the zones again.

Related guide

Specialized Redact PDF guides

Trust & privacy

Local flattening up to 100 MB

Rectangles are drawn and baked in the browser. The download is stem_redacted.pdf.

Covered text on marked pages is destroyed

Those pages are pictures. Proof the download so a missed line is caught before you send the file.