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Redacting PDF areas

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PDF redaction permanently removes sensitive information from a document. Use it when you need to share or archive files without exposing confidential content.

This guide shows how to:

  • Load a PDF
  • Define a redaction rectangle by coordinates
  • Apply permanent redaction
  • Save the sanitized output

Prepare the project

Register the SDK license before running redaction operations. For setup details, refer to the getting started with .NET SDK guide.

using GdPicture14;


LicenseManager licence = new LicenseManager();
licence.RegisterKEY(""); // Set your license key

Load the PDF document

Create a GdPicturePDF instance and load the source file:

using GdPicturePDF pdf = new GdPicturePDF();
pdf.LoadFromFile(@"input.pdf");

Define a redaction region

Add a rectangular region to redact:

pdf.AddRedactionRegion(72, 707, 40, 14);

Parameters use PDF coordinates:

  • X position
  • Y position
  • Width
  • Height

Apply the redaction

Apply all queued redaction regions:

pdf.ApplyRedaction();

This operation removes content inside the defined regions from the PDF structure.

Save the redacted document

Write the redacted output file:

pdf.SaveToFile(@"output.pdf");

Coordinate system reference

PDF coordinates use points:

  • Origin (0,0) — Bottom-left corner
  • 72 points = one inch
  • X axis increases left to right
  • Y axis increases bottom to top

Additional redaction options

Extend this workflow with:

  • Multiple AddRedactionRegion calls before ApplyRedaction
  • Custom redaction colors
  • Text-driven redaction
  • Annotation redaction

Error handling and validation

In production, add checks for:

  • Input file existence and file type
  • Operation status after each call
  • Redaction bounds within page size
  • Post-redaction verification for sensitive fields

For status-handling patterns, refer to the handling errors with .NET SDK guide.

Security notes

Before distribution:

  • Verify that every instance of sensitive content is redacted
  • Confirm that content can’t be recovered through selection or extraction
  • Sanitize metadata if needed
  • Secure both the original and redacted document versions

Conclusion

This workflow redacts fixed PDF areas and generates a sanitized output file for secure sharing.