Is it common for printers to request that PDFs be supplied as separated files when they go direct to plate? A few years ago I worked for a print broker and we'd send files to all our printers as composite file and they'd separate it. Now the last 2 printers I've worked with have both asked that I supply them with separations. Why would they be unable to separate the PDF if it's set up correctly (black + 1 PMS)?