Hey Cameron. Here's another vote for PDF. With regards to additional applications I can strongly recommend adding as a first-class use case electronics design where summoning, displaying, comparing and extracting data from electronic parts datasheets is a huge part of workflow. Specific parts of these documents are typically the focus - eg. schematics, physical package drawings, tables. Adding a local (non-cloud) feature to auto-identify or quick scroll-through those to show them larger without manual zoom/repositioning as per current PDF viewer workflows would win many loyal users and should be feasible to build based upon open source OCR layout analysis engines such as tesseract. You may also consider for UI/UX purposes creating either voice input datasheet <MPN> and/or a popup search box with bangs: !datasheet <MPN>, !diagram <MPN>...