Narrated Ibn 'Abbas:
When Allah's Apostle was on his death-bed and in the house there were some people among whom was 'Umar bin Al-Khattab, the Prophet said, "Come, let me write for you a statement after which you will not go astray." 'Umar said, "The Prophet is seriously ill and you have the Qur'an; so the Book of Allah is enough for us." The people present in the house differed and quarrelled. Some said "Go near so that the Prophet may write for you a statement after which you will not go astray," while the others said as Umar said. When they caused a hue and cry before the Prophet, Allah's Apostle said, "Go away!" Narrated 'Ubaidullah: Ibn 'Abbas used to say, "It was very unfortunate that Allah's Apostle was prevented from writing that statement for them because of their disagreement and noise."
— Muhammad al-Bukhari, Sahih al-Bukhari
This is the so called "Hadith of The Pen and Paper"
According to it, the Prophet (PBUH) requested a pen and a paper to write things. I've always been told that he was an illiterate. Is this the case?
I assume he was an illiterate when Qur'an started to be revealed but learned how to read/write after. Or perhaps the translation is wrong as suggested in the comments. He would rather dictate instead of writing. What is the general stand regarding the illiteracy of the Prophet (PBUH)?