If you've ever drawn a black rectangle over a Social Security number in a PDF and called it "redacted," there's a good chance the number is still in the file. A black box is often just another object sitting on top of the page -- the text underneath hasn't gone anywhere. Anyone who copies the page, selects the text, or opens the file's raw structure can pull it right back out. LockerPDF's Redact PDF tool works differently: it actually deletes the content, not just hides it, and it runs entirely in your browser.
Why a black box usually isn't redaction
Most "draw a box over it" tools -- including the built-in markup tools in PDF viewers and slideshow software -- add a shape as a new layer on the page. The original text object stays exactly where it was, underneath the box, fully intact in the PDF's internal structure. This creates a few well-known ways the "redacted" content leaks back out:
- Select-and-copy. Highlight the area with your cursor, copy, and paste into a text editor -- the hidden text often comes along with it, because the black box was never bonded to the text layer.
- Extraction tools. Any script or tool that reads a PDF's text objects directly (rather than rendering it visually) can pull the covered text out, since it's still present in the file, just not visible on screen.
- Zooming or exporting. Some viewers let you export or print with layers stripped, which can reveal what a box was covering.
This isn't a hypothetical edge case -- it's a recurring, well-documented failure in real redaction incidents, from court filings to government reports, where a black box turned out to be cosmetic rather than destructive. If the goal of redaction is to make sure nobody else can recover the content, covering it with a shape doesn't meet that bar.
How LockerPDF's Redact PDF tool actually removes content
Instead of layering a shape over the original page, LockerPDF's tool rasterizes the page. When you mark a redaction box and click "Redact & Download," every page that has at least one box is rendered to a flat image with the black boxes burned directly into the pixels, and that image replaces the original page in the PDF. The original text and object data for that page is gone -- not hidden, not layered, deleted. There's nothing left underneath the box to select, copy, or extract, because the page is no longer made of text and objects at all -- it's a picture.
Pages you don't mark are left completely untouched. If you redact one paragraph on page 3 of a 40-page contract, only page 3 gets flattened -- the other 39 pages keep their original selectable, searchable text exactly as they were. This is the same rasterization approach behind LockerPDF's Compress PDF tool, discussed in more detail in this post on the tradeoffs of rasterizing a PDF -- rendering a page to an image is a deliberate, disclosed way to guarantee nothing recoverable is left behind, not a shortcut.
The tradeoff: redacted pages lose their text layer
Being flattened to an image is what makes the redaction permanent, but it comes with a real cost: any page you redact loses its selectable, searchable, copyable text. If someone later tries to Ctrl+F for a term that was on a redacted page, or tries to copy a paragraph from it, they won't be able to -- not because it's blocked, but because the page is now pixels, the same as a scanned document. That's the correct tradeoff for a page that contains something you're actively trying to erase, but it does mean you shouldn't redact a page just to be cautious if there's nothing on it that actually needs removing.
Keep your original file. Redact a copy for the specific purpose that needs sensitive content removed -- sharing a contract externally, publishing a document, responding to a records request -- and keep the untouched original for your own records.
How to redact a PDF for free without uploading it
- Go to the Redact PDF tool and drop in your file. Nothing is uploaded -- the file is read and processed by JavaScript running in your browser tab.
- Click and drag over the page to draw a black box over each piece of content you want removed. Use the page navigation and zoom controls to move through a multi-page document and mark content on any page.
- Review the box count shown below the preview, and click the × on any box you want to remove before finishing.
- Click "Redact & Download." Every page with at least one box is flattened to an image with the boxes burned in; pages with no boxes are left untouched.
- Download the result and verify it -- try selecting text where you drew a box. You shouldn't be able to.
You can confirm none of this touches a server the same way you'd verify any privacy claim: open your browser's developer tools (F12), switch to the Network tab, and redact a file. You won't see an outgoing request carrying your document's bytes.
When you actually need this vs. when a black box is fine
If you're marking up a document for an internal review -- pointing a colleague to a section, blocking out a diagram in a screenshot you'll never share as a raw PDF -- a cosmetic box is often good enough, because nobody downstream has a reason to dig for what's underneath. Real redaction matters when the document is leaving your control: filed with a court, sent to an opposing party, published publicly, or handed to someone whose interests don't align with keeping the covered content private. In those cases, the only safe assumption is that if the text is still in the file, someone eventually finds it.
FAQ
Does drawing a black box in a normal PDF viewer actually redact the text?
Usually not. Most viewers add the box as a separate shape layered on top of the page -- the original text stays in the file's structure underneath it and can often be recovered by selecting, copying, or extracting text directly from the PDF, even though it's not visible on screen.
How does LockerPDF's Redact PDF tool actually remove content?
It rasterizes each page you mark -- rendering it to a flat image with your redaction boxes burned into the pixels, then replacing the original page with that image. The underlying text and objects for that page are deleted, not covered, so there's nothing left to select or extract.
Will redacted pages still have selectable text?
No. Flattening the page to an image is what guarantees the covered content is actually gone -- but it also removes the selectable, searchable text from that specific page. Pages you don't mark are left completely untouched and keep their original text.
Is my file uploaded anywhere when I use this tool?
No. Redaction happens entirely in your browser using JavaScript -- your PDF is never sent to a server. You can verify this by checking your browser's Network tab while redacting a file; no request will contain your document's data.