This is the killer feature. Are you confused about the difference between 含む (fukumu) and 含める (fukumeru)? In a physical book, you flip pages for ten minutes. In a PDF, you hit Ctrl + F (or Cmd + F ), type the word, and you are there instantly.
Find 10 sentences from your PDF that use a target word. Delete the word. Next day, fill in the blank without looking. jlpt n2 vocabulary pdf