This could be a bit discriminatory, Brazil has a high analphabetism rate, it will be worst in prison, I suppose.
The ones who can't read should be offered courses and maybe start with easy comics.
I've never heard that word before. It's a synonym for illiteracy.
Some illiterate 'iletrado'(for us) in some cases can read, but might not understand it very well.
That might explain why the OP used the given word because in some languages its the definition that defines people who cant read.
We would be likely to call that second group "functionally illiterate".
Spanish - analfabeto
Portuguese - analfabeto
French - analphabète
Italian - analfabeta
German - Analphabet
Romanian - analfabet
Polish - analfabeta