reply to KahunaNui
Re: USG 20 or 50 the right choice? My guess with Acrobat is that document originators wanted a way to lock documents so that full power Acrobat couldn't be used to modify them. This requires a password so that the originators have access. The more recent Acrobat readers have a way to open such documents in read-only mode, probably without any way to copy parts.
I had to add Acrobat reader to my Ubuntu operated desktop to read the manual. It is good to learn that Foxit may be able to read it now. Acrobat has had some security problems over the years, I'm led to believe, and while for the most part these may not be Linux threats, there is no use trolling for pwning.
I confused Foxit with something else. I don't think it is available for Linux.
Right now I'm experimentally attempting to convert the file using LibreOffice Writer. It has been running CPU4 at 100% for a while now, so the practicality of this, even if successful, seems dubious.
BranoI hate VogonsPremium,MVMReviews:
These files are not password protected, they're just encrypted and can be opened with Acrobat 9 and later as per screenshots here »Re: USG 3.0 User Guide
...every document format is evolving, 3rd party readers need to keep up the pace or they become useless