[skovorodkin]

Reading PDFs on Kindle Paperwhite is much more comfortable with KOReader. Thanks to https://www.willus.com/k2pdfopt/ it can crop pages and reflow text unlike the native reader. It's not the best experience with some types of documents, but generally it works very well.

I don't have a solution for synchronization at this point. My current workflow is quite involved: import a document into Calibre, upload it to Kindle via Calibre wireless connection (KOReader supports it), read and highlight, get the modified doc back to Calibre, extract highlights with https://github.com/0xabu/pdfannots. It'd be more convenient to send new highlights from Kindle somewhere immediately without transferring the document itself. I haven't looked into it, but I believe it should be possible with a KOReader plugin.

[JeremyNT]

Koreader is a great program! It works on touchscreen Linux devices as well.

You might be interested in replacing your paperwhite with a "boox" or "likebook" ereader device. Both of these run Android, so in addition to koreader you can install e.g. syncthing and have a shared directory copied between all of your devices and your own PC.