I have designed several booklets for a customer each targeting a specific audience. Some of these pages are the same like this back cover file which I have made using inDesign and is placed as the last page of all the booklets. When I make a print layout setting up the pages [12/1] [2/11] ... to print as a booklet I place all the pages from the indesign file for each book. This means that my print file references a design file which references a variety of pages and fliers of pdf, ai and indd types. I recently had some upgrades at work which turned off all the fonts managed on a server. Looking at the preview of my print layout file it was obvious that I was needing to activate a font, but inDesign says nothing was missing. I had to open the back cover page file itself before inDesign recognized there was a font problem. This is a very dangerous omission considering if I get in files from a client to print I might not need or want to open their single page originals, but just place them in the order needed to be printed as booklets.