It preserves the page exactly, which is why it looks right everywhere and is awkward to edit. A scanned PDF is only a picture of text until the words are recognized.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
a photograph of the page, not the page itself.
For example
A form looks exactly the same on your phone, the library computer and the printer. That is what it is for, and also why it is hard to change a word.
This is one card out of 275.
The hundred words you meet most are free — the whole set, animated, in one file that works with no internet.
Volume 1 has all 275 in fifteen chapters, with Staying Safe the largest chapter on purpose.