Q) Does PDF/R support multiple pages in a single file?
A) Yes, but that is not its priority
Q) Can PDF/R support encryption or authentication?
A) PDF/R supports password and certificate encryption and multiple digital signatures
Q) What IP restrictions are there in PDF/R?
A) None – it is a strict subset of the PDF specification, open sourced by Adobe
Q) Can regular PDF libraries be used to read PDF/R?
A) Yes
Q) How does one identify a PDF/R file?
A) A PDF/R file is a well-formed PDF file, but has a comment section in its trailer with an identifying string which indicates to a reader that it conforms to the PDF/R subset of the full PDF specification. The intention is that if a PDF/R file is edited using a conventional PDF library which is naive about PDF/R, the resulting file will not have this comment as the last object in the file.