Reading Spanish is hard when every other word stops you. KoruPDF underlines only the words you probably don't know, based on your own level, so a page stops looking like a wall of unknowns. Click any word for a full dictionary entry - IPA, part of speech, examples - or ask why it means that here. Every lookup is tracked: encounter counts, mastery levels, spaced quizzes, CSV or Anki export. A focus mask keeps reading first. All PDF processing is local; nothing you read is uploaded.