Here's how it works. You basically add everything you're reading to Polar.
Right now it supports PDF and captured web pages. It works offline and your data is yours. It's a desktop app with a webapp+mobile coming soon (like 2 weeks).
Polar supports suspend and resume of reading with "pagemarks" which are basically "boxes" covering multiple pages with a start and end.
https://getpolarized.io/incremental-reading.html
This way it's very very clear what you've read and what you have not.
While you're reading you can annotate and take notes directly in Polar.
This includes comments, highlights, but also flashcards.
The flashcards can be sync'd with Anki which means you get spaced repetition built in so you NEVER forget anything.
Here's a screenshot of my current reading:
https://i.imgur.com/jdnuhVB.png
The progress bar on the right is how far I've read within that document.
All your annotations and highlights are yours. We support markdown export and the on disk format is simple JSON.
It's also Open Source and we'll have a web and mobile version soon. Works on Linux, MacOS and Windows.
It also supports cloud sync so if you have multiple computers you can keep all your data in sync.
If you just want to avoid the cloud you can not use the cloud sync.
However, if you do, you can also use the web version which is coming out soon and which also means you can use it on a tablet device.