I've never tried to programatically open a PRF file, but I got the impression with v11 that there were some odd things going on with some of the methods. Can you open a password protected PDF file, for example?
As far as I know, the only program that creates PRF files is Monarch itself, specifically earlier versions of Monarch. Since v10, if you need to export the source report with the table, then the Context add-in for Excel is the supported method, and if you need to export a tree structure to navigate a report, an export of the report to PDF is the preferred method.
That's the official line, but personally, I can see two problems - at my work, we run Excel 2003 and so can't use Context, and I've seen plenty of big data where a tree has more than 65k nodes and so PDF files can't handle all the bookmarks. PRF files were a clever idea to share the benefits of report mining with multiple readers, back in the days of the desktop.
Since the new management arrived at Datawatch, there seems to be a fairly clear strategy to join up Monarch with the server tools in a more organised way. If you want to share a report with a attached model for a team of users, the Monarch Enterprise Server is the supported platform. You get a load of advantages (document level security, browser-based access with no desktop installation, dashboards, annotations and collaboration etc) but you do need a server, and licences for the users you want to share the data with.
Hope this helps,