Every few months a news story shows a court filing or a government report where someone covered names with black bars, and a reader copied the text from under them. The bars were just shapes drawn on top of the page. The words were still there, underneath. If you ever share a PDF with details that must stay private, such as an account number, a home address or a child's name, you need to know the difference between hiding text and removing it.
Why a black box is not enough
A PDF is built from layers of instructions. The text is one instruction, and a black rectangle is another. When you draw a rectangle with a highlighter, a pen or a shape tool, you add a new instruction after the text. The page looks redacted, but the text instruction is still in the file. Anyone can open the PDF, press Ctrl+A and copy, drag the rectangle away in an editor, or run a text extractor and read what you tried to hide.
The same goes for white text on a white background, for text covered by an image, and for a page that was printed to PDF with a rectangle that is a separate object. If the original characters are still stored in the page, the page is not redacted.
What real redaction does
Real redaction removes the content under the box, not just the look of it. There are two common ways. Professional editors such as Adobe Acrobat find the covered text and delete it from the page's instructions while keeping the rest of the page as text. The simpler and very robust way is to turn the page into a picture with the black boxes painted into the picture, and replace the page with that picture. Once the page is an image, there is no text left to extract, because a picture of black pixels has nothing behind it.
DocPro's Redact PDF uses the second method. Each page that has at least one box is drawn at about 200 dpi with the boxes burned in, and that image replaces the page. Pages that have no boxes are kept exactly as they were, so the rest of the document stays selectable and sharp.
How to redact a PDF with DocPro
- Open Redact PDF and choose your PDF. A password-protected file asks for its password on your device.
- Draw boxes by dragging over each area on the page preview. Use the × on a box to remove it, and the arrows to move between pages.
- To catch every occurrence of a word, type it into Find text and press Find and box all. It boxes every match on every page. You can also box all email addresses or long numbers with one click.
- Look at each page again. Automatic boxes are placed from the text positions in the file, and they are padded a little, but you should always confirm that each one covers what it should and nothing is left sticking out.
- Press Redact and save PDF. The new file is built on your device, and DocPro checks that no selectable text is left on the redacted pages.
What changes in the file
Because redacted pages become images, three things change. The text on those pages can no longer be selected, searched or copied. The file may be larger than the original, since each page is now a picture. And bookmarks, attachments and form fields are not carried over to the new file. Pages without boxes keep their text. If you need the redacted pages to be searchable again, you can run OCR to PDF afterwards, which reads the visible text of the pages. The black boxes stay black, so the hidden words are not recovered.
Do not forget the hidden parts of a PDF
Visible text is only one place where private details hide. A PDF also carries document information such as the author's name, the title, the dates and the software used, and sometimes an XMP block and a document ID. DocPro's Redact PDF starts the new file without any of that. If you only want to clean the metadata and leave the pages alone, use Remove PDF metadata. Comments and annotations on a page are drawn into the picture on redacted pages, and the original objects are not copied over.
Keep your original. Redaction cannot be undone on the new file, and you may need the unredacted version later. Name the redacted copy clearly so you never send the wrong one.
A short checklist before you share
- Open the redacted file and try to select text under a box. On a redacted page nothing under the box should be selectable.
- Search the file for the words you removed. They should not appear on redacted pages.
- Zoom in on every box. A box that is a few pixels short can leave the edge of a letter showing.
- Check headers, footers and page numbers on every page, where the same name often repeats.
- Look at the file properties to confirm that the author and title are not filled in.
What redaction does not cover
Redaction protects the content of the file you share. It does not change what you already sent. If an unredacted copy was emailed or uploaded earlier, it still exists. It also cannot help with details that are visible in the redacted version in another way, such as a person who can be identified from the context around the box. Think about what the surrounding text gives away as well.
For documents with legal or regulatory requirements, such as court filings, check what your court or authority expects. Some require a specific redaction process or software, and they may inspect the file. DocPro's redaction is a practical tool for everyday privacy, and you are responsible for checking the result.
Redact an image or a photo
If the private detail is in a photo, such as a face or a number plate, use Blur faces in photos, which can cover areas with a solid block, and Remove photo metadata to strip the location from the picture. To put a clean copy into a PDF afterwards, use Images to PDF.
Frequently asked questions
Can someone recover text from a PDF redacted with DocPro?
Not from the redacted pages. Each of those pages is replaced by a picture with the boxes painted black, so the covered text is not stored in the new file. Keep the original safe, and check the result before you share it.
Why can I not select text on some pages after redacting?
Pages that had a box became images, which is what makes the redaction permanent. Pages without boxes keep their text.