---
title: "Redact text in a PDF"
url: https://recursiveai.org/onepdf/cookbook/redact/
description: "Find a name on every page of a PDF in C#, remove it from the content, cover the spot with a black box, and clear it from the metadata."
version: "1.11.0"
---

# Redact text in a PDF

Find a name on every page of a PDF in C#, remove it from the content, cover the spot with a black box, and clear it from the metadata.

OnePDF removes the text from the file. Nothing is just hidden under a box.

```csharp
using OnePdf;
using OnePdf.Text;

string[] phrase = ["Jane", "Doe"];

using PdfDocument doc = PdfDocument.Open("report.pdf", new PdfOpenOptions { AllowEditing = true });

// Find the phrase on every page and collect the boxes of its words.
var regions = new List<PdfRedactionRegion>();
for (int p = 0; p < doc.PageCount; p++)
{
    PdfPageText text = doc.Pages[p].ExtractText();
    foreach (PdfTextLine line in text.Blocks.SelectMany(b => b.Lines))
    {
        IReadOnlyList<PdfTextWord> words = line.Words;
        for (int i = 0; i + phrase.Length <= words.Count; i++)
        {
            if (!phrase.Select((s, k) => words[i + k].Text.TrimEnd(',', '.', ';') == s).All(match => match))
                continue;
            PdfRectangle[] boxes = words.Skip(i).Take(phrase.Length).Select(w => w.Bounds).ToArray();
            var area = new PdfRectangle(boxes.Min(r => r.Left), boxes.Min(r => r.Bottom), boxes.Max(r => r.Right), boxes.Max(r => r.Top));
            regions.Add(new PdfRedactionRegion(p, area));
        }
    }
}

// Remove what is under the boxes, draw black boxes over them, and clear the name from the metadata.
PdfRedactionResult result = doc.Redact(regions, new PdfRedactionOptions
{
    Overlay = new PdfRedactionOverlay(),
    MetadataTerms = [string.Join(" ", phrase)],
});
Console.WriteLine($"{regions.Count} areas, {result.GlyphsRemoved} glyphs removed on {result.PagesProcessed} pages");
doc.Save("redacted.pdf");                                    // a full save; SaveIncremental is refused after Redact

using PdfDocument check = PdfDocument.Open("redacted.pdf");
bool found = check.ExtractText().Any(page => page.Text.Contains("Jane"));
Console.WriteLine($"\"Jane\" still in the text: {found}");
```

```text
6 areas, 54 glyphs removed on 6 pages
"Jane" still in the text: False
```

`pdftotext` agrees: the first line of the page now reads “Prepared by” and then the account number.

## What is removed

`Redact` rewrites the page content. Inside each area it removes:

- the glyphs whose boxes meet the area,
- vector paths and shadings that meet it,
- image samples under it (the image is blanked there and stored again),
- annotations, and the values of form fields whose widgets meet it,
- `/ActualText` and alternate text of the tagged content it removed.

`MetadataTerms` clears matching entries from the document information, the XMP metadata and bookmark titles. `RemoveJavaScript`, `RemoveEmbeddedFiles` and `RemoveThumbnails` strip those parts too.

## Good to know

- **Save with `Save`.** After `Redact`, `SaveIncremental` is refused, because the old content would stay in the file’s earlier revision.
- **It fails closed.** If any page’s content can’t be read completely, `Redact` throws `PdfRedactionException` naming the page and changes nothing.
- **Areas are in the page’s own coordinates**, before its rotation. Word boxes from text extraction have the rotation applied, so on a rotated page convert them first. On an unrotated page, as here, they can be used as they are.
- **Matching is by position.** Only the places your areas cover are removed. A word drawn in two places needs two areas, and text that exists only as an image, such as a scan without a text layer, is removed only by blanking the image.
- **Signatures** become invalid once the redacted document is saved. `result.SignaturesInvalidated` says so.
- JPEG and other compressed images are blanked when a decoder is registered in `PdfRedactionOptions.Decoders`. Without one, an image that meets an area is removed whole.

The full list of what is and isn’t covered is in [Redaction](https://recursiveai.org/onepdf/docs/redaction/). Finding words is covered in [Get words and their positions](https://recursiveai.org/onepdf/cookbook/word-positions/).

For the whole workflow, including image areas, metadata and checking the result, see [Redact a PDF in C#](https://recursiveai.org/onepdf/articles/redact-pdf-csharp/).