How it works: enter one or more search terms or regex patterns (one per line). Every occurrence on every page is found, then permanently overlaid with a solid black rectangle. The underlying text is also stripped from the PDF's content stream so it cannot be recovered with copy-paste.

Common patterns: \b\d{16}\b (credit-card numbers), [\w.-]+@[\w.-]+\.[\w]+ (emails), \b\d{3}-\d{2}-\d{4}\b (US SSN-like). Plain text is matched literally unless you tick “Treat as regex”.