PDF redaction tool: what a good one does
Published November 3, 2026
A PDF redaction tool removes text from the file itself, not just from view, so nobody can copy, search or extract it afterwards. Free and paid redaction software differ mostly in how they find what to remove, whether they also clear hidden data, and whether they let you check the result before it goes out. This page lists what to look for and how to test any tool on a sample file in a few minutes. It is written by BatesNumbering.app, so read it with that in mind. This is general information, not legal advice.
Removing, not covering
A black rectangle drawn with a markup or shapes tool is a separate object laid over the page; the words beneath it stay in the file. A redaction tool either deletes the letters and draws the box in their place, or turns the page into an image with the box burned in. Both remove the text. The image route also makes that page unsearchable, so a tool that does it only on the pages with a redaction keeps the rest of the file searchable. The ways covering goes wrong are in why black box redactions fail.
Two vendor examples, from their own help pages. Adobe's "Redact sensitive content in PDFs in Acrobat Pro" says marked items are not permanently removed until the redactions are applied and the file is saved, and Acrobat saves a new file with "_Redacted" added to the name. Apple's Preview guide says a redaction in Preview becomes permanent once you close the document. In both, the moment the text is really gone is a step you take, not the moment the box appears.
What to look for
| Feature | Why it matters |
|---|---|
| Search for patterns, not only words | Social Security, account, routing and card numbers appear with dashes, spaces or none. A search for one exact string misses the others. Adobe's Find Text and Redact works on searchable text; Adobe says text in images cannot be searched. |
| Keep the last four digits | Federal Rule of Civil Procedure 5.2(a) allows only the last four digits of a Social Security, taxpayer ID or financial account number in a filing. A tool that can leave the last four saves a box per number. See the court rules on SSNs and account numbers. |
| Hidden information | Title, Author, keywords, attachments, form fields, comments and hidden layers can carry a name or a number that is on no page. Acrobat Pro's sanitize step removes these; Adobe's help lists metadata, attachments and hidden layers among them. |
| A check of the output | Reading the finished file the way the recipient would (text, every pattern again, metadata) is the only way to know what is left. |
| Where the file goes | Some tools upload the PDF to their servers; others work on your device or in your browser. For bank statements and medical records, that is worth knowing before you pick. |
| Scans | A scanned page is a picture. A tool without OCR cannot read it, so it cannot find a number on it. |
Free redaction tools and where they stop
Free tools that remove the text exist: Preview on a Mac and several browser tools, listed with what each one does in how to redact a PDF for free. They are usually enough for one document going to a landlord or a lender (see redacting a bank statement). They stop in three places: they remove only what you mark or what their patterns recognise, they work file by file, and few of them check the result. A side-by-side table of free and paid tools, with prices from each vendor's site, is in Bates and redaction tools compared.
Test any tool in five minutes
- Make a sample file with invented numbers: a Social Security number written three ways (with dashes, with spaces, as nine digits), an account number in a header, and your name in the document's Title.
- Redact it with the tool, the way you would a real file.
- Copy across each box and paste into a plain text editor. Anything that pastes is still there.
- Search the finished file for the last digits you removed, and open the document properties.
- Run a leak check. The free leak check reads the whole file, flags text under boxes and reads the metadata, so it also finds numbers nobody marked. Scanned pages are flagged as not checked.
No tool removes what it does not find, so whatever the tool, someone reviews every page. What to remove in a court filing is set by the court's rules, and a lawyer or the court's self-help center can say what applies to your case.
BatesNumbering.app is a PDF redaction tool that runs in your browser: it looks for Social Security, tax ID, account, routing and card numbers across a whole set of PDFs, can keep the last four digits, flattens only the pages with a redaction, clears metadata, reads the output again before the download, and Bates-numbers the set; the first 10 pages are free and $29 covers a set of up to 1,000 pages.
Common questions
What is the best free redaction tool for PDFs?
It depends on the file. Preview on a Mac and several browser tools remove the text for free. For one document, any of them followed by a check is usually enough; for a large set, the work is finding every number, which free tools leave mostly to you.
Does a PDF redaction tool remove the text or just cover it?
A real redaction tool removes it: it deletes the letters or turns the page into an image with the box burned in. A box drawn with a markup or shapes tool only covers the text, which can still be copied.
Is Adobe's redaction tool in Acrobat Standard?
Adobe's redaction help is written for Acrobat Pro. Its steps are to mark the content, apply the redactions, optionally sanitize hidden information, and save the new file.
Can redaction software find Social Security numbers automatically?
Many tools search for patterns such as Social Security and card numbers. Formats vary, so test the tool on a sample with numbers written several ways and review every page of the real file.
Redact and Bates-number a set of PDFs in one pass →Or check a PDF for numbers left in it, free →
More guides: What is Bates numbering · Bates numbering without Acrobat · Bates number format and examples · Bates numbering a discovery response without a lawyer · Exhibit numbers vs Bates numbers · How to Bates stamp a PDF · How to redact a PDF for free · Redacting SSNs and account numbers in court filings · Redacting a bank statement · Why black box redactions fail · Redacting a PDF on iPhone or Mac · A document production index · Rolling productions · Responding to a request for production · Bates and redaction tools compared · batesstamp.com alternatives · RedactifyAI alternatives · Adobe Acrobat alternatives for Bates and redaction