How to Redact Text in C# PDF with IronSecureDoc

Curtis Chau

Updated: July 21, 2026

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  # How to Redact Text in C&num; PDF with IronSecureDoc In this article, we will discuss redacting text on a PDF using IronSecureDoc. This allows the service or process to quickly and easily redact sensitive information by making a simple `POST` request with the PDF to the running IronSecureDoc server. We will demonstrate this visually through the use of Swagger docs. The `POST` request takes in both required and optional parameters and is highly customizable; the response returns the PDF with the redacted text. <div class="hsg-featured-snippet"> <h2>How to Redact Text on PDF with IronSecureDoc</h2> <ol> <li><a class="js-modal-open" data-modal-id="trial-license-after-download" href="https://hub.docker.com/r/ironsoftwareofficial/ironsecuredoc">Pull and start the IronSecureDoc Docker Image</a></li> <li>Test the API using Swagger</li> <li>Specify the text to be redacted</li> <li>Execute the API call with the provided details</li> <li>Export the redacted PDF document</li> </ol> </div> ## Pull and Start IronSecureDoc If you don't have IronSecureDoc running yet, please follow the links below to get it set up: <table class="table"> <tr style="background-color: rgb(241 249 251);"> <th style="text-align: center;">Host Locally</th> <th style="text-align: center;">Deploy to Cloud</th> </tr> <tr> <td style="vertical-align: top;"> <ul> <li><a href="/enterprise/securedoc/tutorials/hosting-windows/">Hosting on Windows</a></li> <li><a href="/enterprise/securedoc/tutorials/hosting-mac/">Hosting on Mac</a></li> <li><a href="/enterprise/securedoc/tutorials/hosting-linux/">Hosting on Linux</a></li> </ul> </td> <td style="vertical-align: top;"> <ul> <li><a href="/enterprise/securedoc/tutorials/set-up-azure/">Deploy on Azure Container</a></li> <li><a href="/enterprise/securedoc/tutorials/set-up-aws/">Deploy on AWS Container</a></li> </ul> </td> </tr> </table> ## The [POST] Redact Text API The [POST] Redact Text API endpoint allows you to hide sensitive text within a PDF document using redaction. This functionality is essential for applications that handle confidential documents, such as legal contracts, medical records, or financial reports. Using this API ensures that specific text is permanently removed, providing enhanced security and ensuring compliance with data protection standards. [[i:(Once a text is redacted, the content cannot be recovered.)]] ## Swagger Swagger is a powerful tool that enables developers to interact with RESTful APIs through a user-friendly web interface. Whether you're using languages like Python, Java, or others, Swagger offers a convenient way to test and implement this API. ### Steps to Redact Text with Swagger 1. **Access the Swagger UI:** If your API server is running locally, you can access Swagger by navigating to `http://localhost:8080/swagger/index.html` in your web browser.  2. **Locate the [POST] Redact Text API:** Within the Swagger UI, find the `POST` `/v1/document-services/pdfs/redact-text` endpoint.  3. **Specify Configurations:** In this example, I am providing both the PDF file and the words to redact in the `POST` request. We will redact the word "we" and overlay a black box on it. For this demonstration, we will use the '[sample.pdf](/static-assets/securedoc/how-to/redact-text/sample.pdf)' file with the following configurations: - `draw_black_box`: `true` - `match_whole_word`: `true` - `words_to_redact`: we 4. **Upload a Sample PDF:** In the request body, upload a sample PDF file where you want to apply the redaction. Ensure that the file is added as **`pdf_file`**. 5. **Execute the Request:** Click "Execute" to run the request. The response will include the redacted PDF. This Swagger UI interaction allows you to easily test the redaction process, providing immediate feedback. <hr /> ## Use CURL Request through Command Prompt Alternatively, we can use the Command Prompt with a `curl` `POST` request to achieve the same result. ```shell curl -X POST 'http://localhost:8080/v1/document-services/pdfs/redact-text' \ -H 'accept: */*' \ -H 'Content-Type: multipart/form-data' \ -F 'pdf_file=@sample.pdf;type=application/pdf' \ -F 'words_to_redact="we"' \ -F 'draw_black_box=true' \ -F 'match_whole_word=true' ``` [[i:( By default, PowerShell may interpret `curl` as an alias for `Invoke-WebRequest`, a built-in PowerShell cmdlet. Try using `curl.exe` instead of `curl`. ```shell curl.exe --version ``` )]] ### Required Request Body Parameters <table class="table"> <tr> <th style="text-align: center;">Name</th> <th style="text-align: center;">Data Type</th> <th style="text-align: center;">Description</th> </tr> <tr> <td><code>pdf_file</code></td> <td><code>application/pdf</code></td> <td>The PDF file you want to manipulate.</td> </tr> <tr> <td><code>words_to_redact</code></td> <td><code>array[string]</code></td> <td>This parameter takes a list of words and redacts the text matching the input.</td> </tr> </table> ### Optional Request Body Parameters <table class="table"> <tr> <th style="text-align: center;">Name</th> <th style="text-align: center;">Data Type</th> <th style="text-align: center;">Description</th> </tr> <tr> <td><code>user_password</code></td> <td><code>string</code></td> <td>This is required if the input PDF has a user password. The operation will fail if no password is provided for the password-protected PDF.</td> </tr> <tr> <td><code>owner_password</code></td> <td><code>string</code></td> <td>This is required if the input PDF has an owner password. The operation will fail if no password is provided for the password-protected PDF.</td> </tr> <tr> <td><code>specific_pages</code></td> <td><code>array[int]</code></td> <td>Allows you to specify which pages to redact text on. By default, the value is <code>null</code>, meaning the provided word in all the pages will be redacted.</td> </tr> <tr> <td><code>draw_black_box</code></td> <td><code>boolean</code></td> <td>Allows you to specify whether to draw a black box over the redacted text. By default, this value is set to <code>True</code>.</td> </tr> <tr> <td><code>match_whole_word</code></td> <td><code>boolean</code></td> <td>Specifies whether partial matches within words should also be redacted. For example, if the provided word is "are," any words containing "are," such as "hare," will have the "are" redacted as well. By default, this is set to <code>True</code>.</td> </tr> <tr> <td><code>match_case</code></td> <td><code>boolean</code></td> <td>Specifies whether the provided word should be an exact match in terms of case. By default, this value is <code>null</code>. Note: Setting this to <code>True</code> means that lowercase and uppercase strings will not be matched. For example, if the provided word is "WE," the lowercase version "we" would not be redacted.</td> </tr> <tr> <td><code>overlay_text</code></td> <td><code>string</code></td> <td>It specifies the overlay text, such as words or symbols, over the redacted text. By default, this string is empty.</td> </tr> <tr> <td><code>save_as_pdfa</code></td> <td><code>boolean</code></td> <td>Saves the modified PDF with PDF/A-3 compliance. By default, this is set to <code>False</code>.</td> </tr> <tr> <td><code>save_as_pdfua</code></td> <td><code>boolean</code></td> <td>Saves the modified PDF with PDF/UA compliance. By default, this is set to <code>False</code>.</td> </tr> </table> ### Optional Header Parameters <table class="table"> <tr> <th style="text-align: center;">Name</th> <th style="text-align: center;">Data Type</th> <th style="text-align: center;">Description</th> </tr> <tr> <td><code>author</code></td> <td><code>string</code></td> <td>Useful for identifying you as the author of the PDF document. By default, this field is empty.</td> </tr> <tr> <td><code>title</code></td> <td><code>string</code></td> <td>Displays the title of the PDF document. By default, this field is empty.</td> </tr> <tr> <td><code>subject</code></td> <td><code>string</code></td> <td>Useful for identifying the content of the PDF document at a glance. By default, this field is empty.</td> </tr> </table>

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In this article, we will discuss redacting text on a PDF using IronSecureDoc. This allows the service or process to quickly and easily redact sensitive information by making a simple POST request with the PDF to the running IronSecureDoc server. We will demonstrate this visually through the use of Swagger docs. The POST request takes in both required and optional parameters and is highly customizable; the response returns the PDF with the redacted text.

Pull and Start IronSecureDoc

If you don't have IronSecureDoc running yet, please follow the links below to get it set up:

The [POST] Redact Text API

The [POST] Redact Text API endpoint allows you to hide sensitive text within a PDF document using redaction. This functionality is essential for applications that handle confidential documents, such as legal contracts, medical records, or financial reports. Using this API ensures that specific text is permanently removed, providing enhanced security and ensuring compliance with data protection standards.

Swagger

Swagger is a powerful tool that enables developers to interact with RESTful APIs through a user-friendly web interface. Whether you're using languages like Python, Java, or others, Swagger offers a convenient way to test and implement this API.

Steps to Redact Text with Swagger

1. Access the Swagger UI:

   If your API server is running locally, you can access Swagger by navigating to http://localhost:8080/swagger/index.html in your web browser.

   

2. Locate the [POST] Redact Text API:

   Within the Swagger UI, find the POST /v1/document-services/pdfs/redact-text endpoint.

   

3. Specify Configurations:

   In this example, I am providing both the PDF file and the words to redact in the POST request. We will redact the word "we" and overlay a black box on it. For this demonstration, we will use the 'sample.pdf' file with the following configurations:

   • draw_black_box: true
   • match_whole_word: true
   • words_to_redact: we

4. Upload a Sample PDF:

   In the request body, upload a sample PDF file where you want to apply the redaction. Ensure that the file is added as pdf_file.

5. Execute the Request:

   Click "Execute" to run the request. The response will include the redacted PDF. This Swagger UI interaction allows you to easily test the redaction process, providing immediate feedback.

Use CURL Request through Command Prompt

Alternatively, we can use the Command Prompt with a curl POST request to achieve the same result.

curl -X POST 'http://localhost:8080/v1/document-services/pdfs/redact-text' \
 -H 'accept: */*' \
 -H 'Content-Type: multipart/form-data' \
 -F 'pdf_file=@sample.pdf;type=application/pdf' \
 -F 'words_to_redact="we"' \
 -F 'draw_black_box=true' \
 -F 'match_whole_word=true'

curl -X POST 'http://localhost:8080/v1/document-services/pdfs/redact-text' \
 -H 'accept: */*' \
 -H 'Content-Type: multipart/form-data' \
 -F 'pdf_file=@sample.pdf;type=application/pdf' \
 -F 'words_to_redact="we"' \
 -F 'draw_black_box=true' \
 -F 'match_whole_word=true'

curl.exe --version

curl.exe --version

Required Request Body Parameters

Optional Request Body Parameters

Optional Header Parameters

Curtis Chau

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Technical Writer

Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.

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