I believe this PDF is protected by a special non-Adobe plug-in.
First, check that the date on your computer is correct. If it is, then contact the seller of the information, this may be what they set up to happen.
the pdf is dated 2003, my pc is correct 2012 date.
the file was created by a motor manufacter that went out of business in 2005 so cannot contact anyone regarding it
there must be some way to decompile and open it?
Discussions of how to bypass encryption are not permitted on these forums, no matter what the objective.
The file you have linked to is indeed protected with an obsolete encryption plugin that is not part of the normal installation for Adobe Reader.
there must be some way of opening it>?
what plugin is it as may be able to find it and any other adobe product that may work?
The plugin has the internal reference "CSML" - it is not on the list of currently-available plugins for Acrobat and Reader and it appears to have been discontinued shortly after your file was created.
There is no way around this protection mechanism, the contents of the file are encrypted with an algorithm that only the plugin understands.