Couldn’t agree more! Got really excited (OK, maybe I’m marketing nerd..) to find the Sales Documents tool, so we uploaded a couple of docs, tested it out and whilst a shame it doesn’t offer the flipbook view option, the insights were great. So off we went to swap out the links in our marketing emails currently pointing to the flipbook equivalent on our website to the new docs in HubSpot.. only to find they weren’t in the file manager
Clearly you can add docs in file manager on the marketing side, but (i) there are no insights and (ii) you don’t want the same doc in two places - not least in case one gets updated and the other doesn’t, but also as you’d have separate stats for the same doc in two different places.
Seems the same frustration exists from the other perspective here..
Come on guys - please fix it for us..! 
Thanks.