People use 'password-protected PDF' and 'encrypted PDF' interchangeably. They are linked but not identical.
Here is what each actually means.
PDF password
A password that the reader prompts for. Two flavours: an 'open' password (must enter to view) and a 'permissions' password (controls printing, copying, editing).
PDF encryption
The mechanism behind the open password. Modern PDFs use AES-128 or AES-256 to encrypt the file's content. Without the password, the encrypted content is unreadable.
Permissions only
Some PDFs have permissions restrictions without an open password — anyone can read, but printing or copying is blocked. These restrictions are easier to bypass than open-password encryption. Treat them as a courtesy, not a security measure.
Best for…
Open password + AES-256 for genuine confidentiality. Permissions only as a polite restriction. Password-protect-pdf handles both.
FAQ
Is AES-128 enough?
Yes for most cases. AES-256 is stronger and the default for sensitive documents.
Can I remove a password I know?
Yes — open the file, unlock-pdf, and save without password.
Are permissions secure?
Not really — they are a polite restriction, not real security.
For real confidentiality, open-password with AES-256. Set it in Flint.