Agenda - Pathways evaluation forms have security lock - can't open

This has happened to me several times and it seems only to happen when I copy a Pathways Evaluation form from the agenda in FTH. The form is PDF fillable and I complete it (everything is going well) - then when I go back in to update it - I can't because it's asking for a password, it won't open.  I've looked at the file and it says I have read and write access but that it is security encrypted. Has anyone complained about this before?  I can't get around it in adobe acrobat or with anything I try. The message says it's from an unknown developer.  Do you have any idea what password it might be asking for? I've tried my computer password, my apple password, my FTH password. Nothing works. 

I've just noticed a similar behaviour.
The way I overcame it on Windows:

1. Save the blank document before making any 'online' changes.
2. Edit and save.   

After that you can edit and save again.