Gordo,
You can create a certificate and/or a password from scratch, you can even add a digital signature, hidden or not. In essence the certificate pfx is created in Documents and settings...User name...Application Data...Adobe etc.
A person can manipulate the adobe file only and only if he has the pfx on his comp. You can share this pfx only to a specific person, and this pfx is unique. If you want to share to 5 persons your adobe doc, you can create 5 different pfx files, with different passwords.
In essence, the owner of this certificate can use the adobe doc and the certificate as he wants as long he is a legal owner of the adobe document.
Only a humble advice, you migh ask on a adobe forum.
Well...I hope it is useful to you. You have not shared the exact aim of your ask, nor more specific details. If it is something personal or inside an organization et al. If it is something related to business, you might use professional tool for securing the adobe files.
Ok...it seems that from January I must find a job related to web design or desktop help or so. Until that time I flee from this city and stay in a remote place where it is so silent and peaceful. The silence is broke only by the exact rhythm of a few wood-peckers and the snow and the green purity are garments for the old firs, which invite, by their moves, to prayer.
marian+