A black box is not a redaction

You need to send a bank statement to a landlord. They need to see your salary credits. They don't need your account number, your tax ID or your phone number. So you open the PDF, draw a black rectangle over each one, save, and send.

There's a good chance every one of those details is still in the file.

Why the box doesn't work

A PDF isn't a picture of a page. It's a set of instructions: put this text here, in this font, draw this line there. When most PDF editors let you "draw a box", they add one more instruction on top: draw a black rectangle here.

The text underneath is untouched. Anyone who receives the file can:

• Select and copy it. Drag across the black box and paste. The number appears.
• Search for it. The PDF viewer's search finds text under boxes just fine.
• Remove the box. Any PDF editor can delete the rectangle and reveal what's under it.

Scanned documents have their own version of this problem. Many scanners and phone apps add an invisible text layer so the scan is searchable. Black out the image, and that hidden text layer can still be there.

What else travels with your file

Even when the visible text is handled, documents often carry extra baggage:

• Metadata: author names, software used, sometimes file paths from your computer.
• Comments and tracked changes in documents converted from Word.
• Earlier versions: some PDFs save edits by adding to the file, so older content remains inside it.

What real redaction looks like

Real redaction means the private information is gone from the file you share, not hidden on top of it. There are a few ways to get there, and they're not all equal. Ombly takes the most thorough one:

1. It turns every page into a picture, exactly as it looks on screen.
2. It paints the parts you chose solid black, in the picture itself.
3. It builds a brand-new PDF from those pictures alone.

Nothing from the original file is carried across. No text layer, no metadata, no comments, no old versions. If you try to copy text from the result, there's nothing to copy.

There is one trade-off: the shared copy isn't searchable or selectable. For a document you're handing to someone else, we think that's the right call.

A quick check you can do today

Before you send a "redacted" PDF, open it, press Ctrl+A (or ⌘A on a Mac) to select everything, copy, and paste into a plain text note. If you can read anything you meant to hide, so can the person you're sending it to.

Share the document. Keep the secrets.

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