First, some backgrounds. PDF contains two passwords - user and owner. Any of them can be used to open document, and if user password is empty string, it is used by default.
If user and owner password are equal (or owner password is empty), PDF file always opened with user password.
When document is opened with user password, you will have only permissions which was specified during document creation.
If you know owner password, you can open it using this password (if user password isn't empty), or you can switch to this password on "Security" page of document properties.
When owner password is used you have all permissions for this document.
1. PDF-Xchange Viewer Pro (cannot) change a password after opening an existing password protected document ?
2. The File | Document Properties | Security | Security Method (Change Settings) is not available to change an existing password or posses 'any' functionality ?
3. If #2 is correct, why is the "Change Settings" button there?
For now you can only switch to use owner or user password, but changing password or permissions still not supported. This feature will be added into build 42 or 43 of the viewer.
PDF-XChange Co Ltd. (Project Director)
When attaching files to any message - please ensure they are archived and posted as a .ZIP, .RAR or .7z format - or they will not be posted - thanks.