Redact PDF
betaBlack out text and pictures — and remove the words underneath from the file, not just cover them
How it works
Open the PDF and press Redact (X). Drag over anything that must go, on as many pages as needed, or select text and press Mark the selection; marks show as red-edged black boxes and can be removed with their × until you apply. Apply redactions rewrites each marked page: every glyph whose box meets a mark is removed from the content stream (what is left keeps its position), comments and form fields in the area are deleted, and a black rectangle is drawn. Pictures and vector drawings under a mark are covered, not removed, unless you tick Flatten marked pages to pictures, which replaces each marked page with a rendered image at 200 pixels per inch — then nothing underneath survives, at the cost of that page's selectable text. Hidden OCR text layers are redacted too. Save under a new name and check the result with Copy all the text.
Questions
Is the text really gone, or just hidden under a box?
Gone from the page's content: the glyphs are deleted, not covered. You can verify with More → Copy all the text, or by searching the saved file. Pictures need the flatten option to be removed rather than covered.
What about metadata and comments?
Comments in a marked area are deleted with it. Document information (author, title, keywords) is separate: remove it in the Info tab or with Compress → Remove metadata.
Is my file uploaded?
No. Everything runs in your browser — pdf.js draws the document and pdf-lib rewrites it in a background thread — and Save writes to your disk or downloads a copy. Nothing leaves your device.