PDF permissions: what they really do

PDFs can carry flags that say "no printing" or "no copying." They are worth understanding — mostly so you know how little they actually enforce.

Permissions are requests, not walls

These flags ask the reader to disallow actions. A cooperative reader honours them; a determined one ignores them. They deter casual copying, not motivated users.

The owner password

Permissions are tied to an owner password. Anyone with it — or the right tool — can change the flags.

When you need real control

To actually stop someone reading a file, encrypt it with an open password. Permissions alone are not security.