Seeing as how the Studio API is useful for accessing Bluebeam Revu from the "Back End" (i.e. programmers can do useful things without the PDF User / "Viewer" ever being able to manually perform them), I believe it would be extremely beneficial for a new "Front End" API that would allow developers to create custom Menus / Toolsets / Actions so that the human being viewing the PDF can invoke custom actions.
This would be a huge improvement coming from the Engineering community (among many others) since so much of what we as humans do every day for work is to INTERPRET information from a PDF and ACTION that information in some way. I am a firm believer that the fewer programs that any user has to navigate through will greatly increase productivity. Allowing developers to customize the "front end" of Revu would greatly reduce the amount of navigating that users interpreting information from PDFs would have to do.
TL;DR
We should be able to create custom Menus / Tools / Actions within Revu to save PDF users time by reducing the amount of navigation & data management they need to perform currently.
(Javascript scripts don't count, this would be application-level based, not document-level based)
