HR sends over the offer letter. You need to redact your salary before forwarding it to your partner. You drag a black rectangle over the number and email it. Anyone who selects-all the text in that PDF still copies the salary out. The rectangle was just a sticker.
Real redaction means removing the content, not hiding it.
What proper redaction does
Proper redaction replaces the underlying text and image data with nothing — or with a redaction marker that's part of the document stream. The content is *gone* from the file, not just visually obscured. Select-all-and-copy returns blank. Open the file in a text editor and the original characters aren't there.
The visible appearance is usually a black bar in place of the redacted content, but the visible appearance is the receipt, not the security.
How Flint redacts
Open Flint's redaction tool, drop in the PDF, and mark the regions to redact. Flint removes the underlying text and image data, replaces the region with a redaction marker, and produces a clean output file.
Verify by opening the redacted PDF and trying to select the redacted areas. If nothing copies out, redaction worked. If the text is still there, it didn't.
What to redact
Personal data: names, addresses, dates of birth, national IDs, employee numbers.
Financial data: account numbers, transaction details, salary figures.
Legal data: privileged communications, identities of confidential witnesses, settlement amounts.
Medical data: patient identifiers, conditions, test results not relevant to the recipient.
For each, ask: does this person need this specific piece of information to do their job? If no, redact it.
Redaction is destructive
Once content is properly redacted and the file is saved, that content is gone from the redacted copy. You can't undo it. Always work from a copy and keep the original safe.
For batches of similar documents (say, redacting a column from a hundred invoices), automate carefully and audit a sample manually before releasing.
FAQ
Can someone reverse a properly redacted PDF?
No, if the redaction was done by a tool that removes the underlying data. Cover-with-a-rectangle redaction is reversible; true redaction isn't.
Does Flint do true redaction?
Yes. Flint's redaction tool removes the underlying text and image data, not just adds a visual cover.
What about metadata?
Metadata (author, title, software) can leak information too. Strip metadata before sharing — most PDF tools have a 'remove metadata' option.
How do I know it worked?
Open the redacted PDF, try to select-all and copy the redacted areas. If the clipboard is empty for those regions, the redaction is genuine.
Don't ship a PDF with a sticker over the bad part. Redact properly in Flint.