How secure are password protected PDFs that are created with Preview? I use 1Password1 to store not only my own information, but also my sisters home Wi-Fi information.

Since she does not have a 1Password licence, I printed out the information for her to store in a safe place. Now, I was just thinking of using the printing dialog (under "Security Options...") to create a "password protected" PDF.

But what does that actually mean and how secure is it? 


Does this encrypt the whole PDF?
What encryption is used?
Is it compatible with Windows and Ubuntu? 


There does not2 seem to be a knowledge-base article on support.apple.com. The info dialog in Finder merely says that the PDF is "Password Encrypted".
The last Time I checked a 128 bit RC4 encryption of the whole document was used. Also, compatability should be vested.

Here's a screenshot of the output of GuaPDF: