PDF Encryption

I am trying to find out how securely Preview encrypts PDF files. For example, does Preview use 128 or 256 bit encryption? How long can the PDF file password be? How secure are PDF files when encrypted with Preview?

All the info I’ve found is 3+ years old, so looking for something more recent. Thx.

MacBook Pro 15″, macOS 10.14

Posted on Mar 23, 2021 4:39 PM

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1 reply

Mar 23, 2021 4:44 PM in response to pomme4moi

Password-protect a PDF in Preview on Mac - Apple Support

It's secure enough.

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PDF Encryption

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