- let the user upload a PDF
- serve it back to users (maybe through 'sendfile' for consistent naming, see documents app)
- display a thumbnail
ideally cut it up into JPGs
- and use a fancy viewer if there's time (alternatively: outsource this to a new issue).
For the thumbnail, see conclusions that come out of #2 (closed) (potentially a dependency that is able to turn the uploaded PDF into a JPG front cover).
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information