Drop a PDF here and listen to it.
The page stays exactly as it looks, and the words light up as they're read. Double-click any word for its meaning, straight from a dictionary built into this file. Nothing leaves this laptop — the file is opened in your browser, not uploaded, and no part of it needs the internet.
PDF or plain text. Whatever you open is kept here on this laptop, with your place in it, so you can pick it back up later. A scanned PDF has no text layer, so it needs OCR first.
Word meanings come from English Wiktionary (CC BY-SA 4.0), via kaikki.org.