update introduction about redaction

Author: tony-xlh

introduction/index.md

@@ -21,6 +21,8 @@ Dynamsoft Document Viewer does not rely on any external third-party JavaScript l
 
 Dynamsoft Document Viewer is designed to work seamlessly across different browsers and platforms. It is compatible with major browsers like Chrome, Firefox, Safari, and Edge, ensuring a consistent user experience. Additionally, it supports various operating systems, including Windows, macOS, Linux, iOS, and Android, allowing users to access documents from any device.
 
+The SDK's [redaction](/features/datamanagement/annotmanagement.md#redaction) feature goes beyond visual masking - it permanently removes the underlying data from the document. This ensures that sensitive information (PII, classified text, financial data) cannot be recovered or leaked, making it ideal for industries with strict compliance requirements like legal, healthcare, and government.
+
 ## Supported File Types
 
 Users can open, edit, and save PDFs, as well as images in various formats, such as JPEG, PNG, and TIFF.
@@ -36,6 +38,7 @@ Dynamsoft Document Viewer supports a variety of annotation types to enhance docu
 - shape
 - stamp
 - freehand drawing
+- redaction
 
 ## Data Management Concepts