Prevent accidental edits: permissions password. Limit who can read: open password.
Tick whether printing and copying are allowed, understanding these are advisory.
Open the result in a different application and confirm it asks for the password and refuses copying.
An open password is required to open the file at all. A permissions password controls whether printing, copying and editing are allowed. Plenty of people set only the second and are surprised that anyone can still read the document.
The permission bits in the PDF spec are a gentleman's agreement: mainstream readers honour them, while screenshots, image export and scripted parsing walk straight past. Real protection means not sending the original — rasterise it, watermark it, or hand over paper.
An open password can only be recovered by guessing — there is no backdoor. A permissions password is routinely removable, because the content itself was never encrypted.
You set a permissions password, not an open password.
No. It raises the effort, nothing more. Once the file is out, the content can be captured.
Not while encrypted — the pages cannot be read. Decrypt first.
An open password cannot be recovered, only attacked. Permissions passwords are usually removable.