Privacy here means local bytes — not “we delete in 2 hours”
Many converters advertise HTTPS and auto-delete. That still means a copy existed on their disk. Convertify4u Instant stamping uses pdf-lib in a Web Worker: the confidential PDF is not uploaded, so there is no retention policy to argue about. Use this spoke when policy language is “do not send to third-party processors.” You must still be authorized to handle the file. A CONFIDENTIAL overlay does not encrypt, redact, or stop screenshots. Pair with Protect PDF for passwords and Redact for hidden text. Opacity high enough to read on a printout, low enough to read the body. Keep an unmarked original in your records system; circulate only the stamped derivative. Premium batch still runs locally — it is memory, not a sudden cloud hop. If a page is a scanned image, the overlay sits on the picture; that is expected.
What Instant privacy is not
It is not a promise about your own laptop malware, shoulder surfing, or the email you send after download. It is a promise that Convertify4u does not get a copy on this path.
When this spoke versus the hub
The hub is the general stamper. Stay here if you need the no-upload story spelled out for a security review or a nervous client.
After you stamp
Send through your existing secure channel. Compress if needed. Do not re-upload the result to a different “free PDF” site for a second trick.