They're overlaying text that's transparent. It appears you can highlight but you're just highlighting the invisible text. Loaded it up in acrobat and if you add

They're overlaying text that's transparent. It appears you can highlight but you're just highlighting the invisible text. Loaded it up in acrobat and if you add any text styles its pretty obvious then whats happening. At least, that's my working theory. Edit: If you open in google docs it's fine, just formatted wrong.