How to Permanently Redact a PDF (So Text Can't Be Copied)

Why a black box is not a redaction

A filled rectangle or a thick black highlight hides a line on screen, but the text layer underneath is still there. Anyone can select the covered area, copy it and paste the words somewhere else. Court guidance for lawyers warns about the same problem: the Northern District of Alabama says edits made with graphic and commenting tools can be removed by anyone to reveal the text underneath, and that turning text white only makes the words seem to disappear (Proper Redaction Techniques).

A real redaction takes the content out of the file, not just out of sight. Remember the parts of a PDF you do not see on the page, too. Adobe separates redaction, which removes visible text and graphics, from sanitizing, which removes hidden data such as metadata and embedded content (Redact and sanitize PDFs in Acrobat Pro).

Redact a PDF with Docubox

Docubox's Redact PDF does not cover text; it builds a new file that carries no text at all. It draws each page as a picture, paints the areas you mark solid black in that picture, and builds a new PDF from the pictures alone.

1. Sign in first. The editor shows you images of your own pages, so Redact PDF asks for a free account before anything is displayed. You can use Google or a code emailed to you; it costs nothing and you never set a password.
2. Upload the PDF and let the pages render. Add your PDF and select Run Redact PDF. Docubox draws every page on its servers for the editor and shows how many pages are done. Nothing is removed at this stage.
3. Mark what to remove. Drag across a page to draw a box. Click a box to delete it, or use Undo last region. If you cannot use a pointer, choose Add a region by numbers (keyboard) under the page and enter the box as percentages of the page.
4. Select Export redacted PDF. The button stays off until you have marked at least one area. Docubox then builds the new file, and the result page offers Download and Save to my documents.

Drawing the pages and exporting them each count as a conversion against your allowance. A longer document can be cut into parts with Split PDF and redacted part by part.

What the exported PDF contains

Only pictures of your pages. Docubox draws each page the way a PDF viewer shows it, fills the marked boxes with black pixels and writes a fresh PDF with one image per page, at the original page size. Nothing else is carried over from your file, which means the export has:

• no text layer, so nothing can be selected, searched or copied, including the parts you did not mark;
• no links, form fields, bookmarks or attachments;
• no document properties, so the title and author fields are gone as well;
• comments and filled-in form fields only as pixels, drawn the way a viewer shows them, so a box covers them like anything else on the page.

Docubox checks its own work before offering the file. Each marked box has to be solid black in the page image. The finished PDF must have no text, fonts, form fields, comments, properties or bookmarks, and no embedded objects other than images, and the center of every marked area has to render black. If a check fails, the export fails and you get no file.

The editor exports at one fixed resolution; there is no setting to change it. A page too large to draw at that resolution within Docubox's limits is drawn at a lower one, and the result page tells you which page.

Check every page before you send it

Those checks confirm the file has no text and your boxes are black. They cannot tell whether you marked everything that needed hiding. The tool removes exactly what you mark and does not search for names, numbers or addresses on its own.

• Read all of it. Go through every page, including headers, footers, margins and small print, and look for the same detail repeated elsewhere, such as a reference number in a footer.
• Be generous with boxes. Cover the whole word and the full height of the line, so no edge of a letter is left showing.
• Test the downloaded file. Zoom in and read each page, then try to select text anywhere on it. In a Docubox export there should be none.
• Check the file name. The export is named after your original with -redacted added. Rename it if the original name gives away what you hid.

Trade-offs

• Nothing is searchable. Every page is an image, so the text you meant to keep cannot be searched or copied either.
• The file can grow. Page images can take more space than the text they replace, so the export may be larger than the original.
• Small print can soften. The export is not a lossless copy of your pages, so fine text may look less crisp.
• Accessibility suffers. Tags and other accessibility information are not carried over, and with no text layer a screen reader has nothing to read aloud.

Other ways to redact

Adobe Acrobat Pro has a dedicated Redact tool. Adobe says redaction there is permanent once applied and saved, with the redacted content replaced by colored boxes (Adobe). You choose All tools > Redact a PDF > Redact text and images, mark the content, select Apply, and can switch on sanitizing to remove hidden information before you save (Redact sensitive content in Acrobat Pro). Acrobat can also search a document for words, phrases or patterns to redact (Search and redact text in Acrobat Pro), which Docubox cannot do. If you already have Acrobat Pro, it is the better choice for long documents and for redaction you do often.

Preview on a Mac has a redaction tool in its Markup toolbar. Apple says you can change a redaction while you edit, that it becomes permanent once you close the document, and that table-of-contents entries linking to redacted text are not removed (Annotate a PDF in Preview on Mac).

If you created the document yourself, the cleanest option is to delete the information from the source file and export a new PDF. Whichever route you take, open the saved file and try to copy text from inside a redacted area before you share it.

What happens to your files

Docubox renders and rebuilds your pages on its servers; the editor in your browser only displays the page images and sends back the boxes you drew. Your PDF is held in private storage, and Docubox's systems have access to it while the pages are drawn and rebuilt. For a document you cannot upload anywhere, use a desktop tool such as Acrobat Pro or Preview.

Your original PDF can never be saved to your documents, so it always expires; the redacted export is the only file you can save from a redaction. A download neither removes a file nor gives it more time. The help article on redacting and the retention policy cover the rest.