Redact a PDF for free, and check that it's really gone.

01Why a black box isn't redaction

A PDF page is a list of drawing instructions. A rectangle drawn over a paragraph is one more instruction, added after the text: the text is still there, still selectable, still found by search, still in the file for anyone who deletes the box or opens the file in a text editor. The same goes for a highlight set to black, a picture pasted over a line, or text whose color was changed to match the background.

And the page is only part of it. A PDF also carries document properties and XMP metadata, comments and their appearances, form field values, bookmarks, attached files, hidden layers, scripts, and, when it was saved incrementally, every earlier version of itself. A name removed from the page can live on in all of them. That is why Inkvolt PDF treats redaction as two steps: remove, then check.

02Redact in Inkvolt PDF

1. Open the PDF and choose Redact on the command bar, the Redact card on the start page, or type "redact" in the command palette (Ctrl+K). The redaction bar appears over the page.
2. Mark what goes. Drag over an area of the page; or select text and mark it; or search for a word and mark every match at once; or use Redact by Pattern… (below). Marks show as outlines you can review. Click a mark with the redaction tool to keep that text after all.
3. Apply. The text and images under each mark are removed from the page content, not covered. A page with redactions is drawn again as an image at 300 dpi, and the text that remains is put back by OCR as an invisible layer, so the page can still be searched and selected.
4. Read the check. After Apply, Inkvolt PDF checks the result in the background for anything left of what you redacted. A toast says when nothing is; otherwise a report opens with each finding, where it is, and a Fix button.
5. Save, as a copy if you want to keep the original. The file is rewritten as one version, so earlier versions kept by incremental saves are gone too.

A redacted file can't keep its digital signatures: the file is rewritten, so they no longer verify. Inkvolt PDF says so before saving. Sign after redacting, not before.

03Redact by pattern

Redact by Pattern… (Review menu, the command palette, or the redaction bar) finds and marks, across all pages or a range: US Social Security numbers (leaving out the impossible ones), phone numbers (North American and international), email addresses, payment card numbers (only those that pass the Luhn check), dates in the common written and numeric forms, bank account numbers (IBANs, check digits verified), IP addresses and, when you choose, US ZIP codes. Add your own words and phrases (whole words, match case) and your own regular expression, checked as you type. A match that runs onto the next line, or is split by a hyphen at a line break, is still found. The toast counts the matches of each kind; review the marks, keep any you want, then Apply as usual.

Redact by Pattern reads the text layer, so run Recognize Text (OCR) first on a scanned document. Month names are English.

04Check a PDF someone else redacted

Review › Check Redaction… checks any PDF, including one redacted in another app. It looks for:

• text still under black boxes, highlights, other comments or covers, or drawn in the color behind it (each character is drawn and looked at);
• pictures and drawings still under a dark box (the page is drawn again without the box);
• redaction marks that were never applied;
• text beside a box that keeps its original positions, so the width of what was removed can be measured;
• the redacted text anywhere else: other pages, hidden layers and text outside the page, comments and their appearances, form fields (and XFA data), bookmarks, document properties and XMP, attached files (also inside zipped Office files and attached PDFs), tags and alternate text, scripts, objects nothing uses, earlier versions kept by incremental saves, and the file's raw bytes.

Each finding says where it is and how it can be fixed. Fix redacts the areas, sanitizes the kinds that hold leftovers, rewrites the file as one version and checks again. Batch has the check as an action: a file with findings fails, so a folder of redacted files can be checked at once.

The check finds text that doesn't show by drawing it, so a cover that lets a few pixels through counts as shown. On a file redacted elsewhere it doesn't know what was removed, so it looks only for what covers and earlier versions give away. An encrypted file's raw bytes aren't searched (they are ciphertext), its objects are.

05Before you share

Redaction removes what you marked. Two more tools cover what you didn't know was there. What's in This PDF… (Review menu) is one report of everything a file carries besides its pages: scripts and what they reach, web addresses, attachments, metadata, comment authors, signatures, earlier versions with the text they showed, hidden layers and hidden text, form values. Sanitize Document removes those kinds by your choice, counts what it found, rewrites the file as one version and reads the result back to list anything left. What's hidden in a PDF goes through both.

06On the Mac

Inkvolt PDF for Mac (1.1 and later) has the same redaction: areas, selected text, search matches and patterns, the review of marks, Apply, and the check afterwards; Tools › Check Redaction… checks any PDF, and Sanitize Document is there too, with What's in This PDF since 1.2. It is a notarized download for Macs with Apple silicon on macOS 15 or later: download the disk image, or brew install --cask gabandres/inkvolt/inkvolt-pdf.

07Questions

Adobe, Acrobat and Acrobat Reader are trademarks of Adobe. Inkvolt is independent and not affiliated with Adobe; the names are used only to compare.