PDF usually has two types of passwords:
One is to protect the contents of the file from illegal viewing. This password means that as long as you want to open this PDF file, you need to enter the password, otherwise you can't open it.
The other is to protect the content of PDF from illegal tampering and dissemination (that is, to protect its corresponding rights). You don't need to enter a password when opening a PDF, but you need to enter a password when modifying PDF content, marking a PDF, printing a PDF, etc.
As shown in the figure below:
You should have set the first password in the picture above (that is, the second password mentioned above, and you must remove all the checkmarks in the check box before the password will take effect), not the file opening password.
So you will only be asked to enter the password when you need the corresponding permission.
As for where to enter the password, it is usually at? File "Document Properties" security? Only when you modify the internal security settings will you be asked to enter the password. The PDF reader I use is PDF-Xchange? Viewer, enter the password as shown in the figure below:
Above.
Well, it's been a long time. ...