Thanks Eugene for your quick answer.
My file is for a chinese suppliers.
Sometimes, they open pdf files in Illustrator and they make a mess in (changing the font, ...) !
So, I need to send them a simple file, fixed (like a jpg, but in pdf) because it's easier to print for them.
And with a password, I'm worried they don't understand, why the file need a password. I have to make simple with them, very simple.