As a long time user of Libreoffice and having an interest in Documentation formats/workflow, I found the feature to embed ODF docs in a PDF interesting:
https://wiki.documentfoundation.org/Faq/Writer/PDF_Hybrid
It’s a neat feature, but not obvious to me yet in what scenarios this might be useful – especially an engineer where we are used to dealing with source (code, schematics) → output (SW binary, PCB gerbers) workflow scenarios. Perhaps it fits well in the scenario that most people work in – emailing document attachments around in an uncontrolled manner …