I work for a Non for profit organisation and with industry assistance we develop and publish a suite of National Codes in Adobe Acrobat format on CD's. Our association derives a modest income from Codes Sales and in order to protect our intellectual property I'd like to know if there a way to limit the number of PC's the PDF files can be downloaded to. Is it also possible to establish a multi-user agreement and nominate the number of lisensees at the time of purchase.
The only way you could possibly do that would be to operate a digital rights management server (such as Adobe LiveCycle Rights Management Server) and individually assign each copy to a nominated user. There's no "group" licensing model in the DRM software available for PDF files as there's no way for Acrobat or Adobe Reader to know how many other copies may be in use at any one time.
DRM solutions are extremely expensive, so it's unlikely the cost of running the system would be justifiable against the potential lost revenue from piracy. You'd be paying a large five-figure USD sum just for the server license, then the salary of the person administering it.