Dr Sayyid `Abd al-Latif claims that it is possible to prove, through historical facts and traditions, that the Prophet (SA) used to read and write. He supports this by two facts.
(1) He states: "Al-Bukhari relates within the narrations and ahadith recorded in the Chapter: "Al-Ilm" (the knowledge that the Prophet (SA) gave 'Ali, his son-in-law, a secret letter and told specifically not to open it, but have the name of the recipient in his mind and hand him over the letter. Who else other than the Prophet could have written the letter while even 'Ali, his son-in-law and his trusted person did not know its content?  Unfortunately, the narration in Sahih al-Bukhari does not mention 'Ali's (AS) name as the carrier of the letter, whereas Dr `Abd al-Latif concludes that the Prophet (SA) himself had written the letter, on the basis that he kept its contents a secret even to 'Ali (AS):
In Sahih al-Bukhari, Chapter "Al-Ilm" Al-Bukhari asserts: "The Prophet set off a group of people and handed a letter to their commander and asked him not to open it before he arrived at a certain place."
He does not say that their commander was 'Ali (AS). The contents of the narration reveal, in addition, that the one to open it should have been the carrier of the letter not a third person, as assumed by Dr `Abd al-Latif. What Al-Bukhari has narrated is really connected with a story called "Batn al-Nakhlah" recorded in books of history and Prophetic traditions.
Both Ibn Hisham's "Sirah " (under the title: `Abdullah ibn Jahsh's sariyyah) and Bihar al-Anwar  relate the same narration that the carrier of the letter was `Abdullah ibn Jahsh. It is said that the Prophet (SA) asked him to open the letter after two days' journey and do as it instructed, and he did so and acted upon the Messenger of Allah's command.
Al-Waqidi's "Al-Maghazi" states in explicit terms that Ubay ibn Ka'b was the writer of the letter, not the Holy Prophet (SA). It says:
"Abdullah ibn Jahsh said: `Once, after the Salat al-Isha' (night prayer), the Prophet asked me to come to him the next morning early, armed and ready, to be sent on a mission. The next day, after the Salat al-Fajr (morning prayer), held in the mosque in congregation under the leadership of the Prophet, I was standing near the Prophet's house armed and prepared. Some other Companions were present there too like me. The Prophet summoned Ubay ibn Ka'b and ordered him to write a letter. Then, he handed me over the closed letter and said: `You are the commander of these people. Open this letter after two nights of journey on the mentioned path, and act as it instructs.' I did what I had been told after two days and noticed that I had been ordered to go to Batn al-Nakhlah (a place between Makkah and Waif) to obtain necessary information about the Quraysh's caravan. In addition, I had been advised not to compel any of the men to accompany me in the task. Of course, it was a dangerous mission. I told my friends that whoever is ready for the martyrdom could accompany me, and that the remaining were free to go back. They all unanimously remarked: We all heard and shall obey Allah, His Prophet and you.' 
Accordingly, what Dr `Abd al-Latif has based his claim on is totally unfounded.
(2) Dr `Abd al-Latif further states: "As narrated by Al-Bukhari and Ibn Hisham..., the Prophet (SA) wrote the treaty by his own hand."
Firstly, Al-Bukhari has quoted this in one narration and has related the contrary in another. Secondly, Sunni scholars have almost unanimously asserted that although Al-Bukhari's statement apparently indicates that the Prophet (SA) himself has written it, this has not been the intention of the narrator. Al-Halabi's "Sirah", narrates the story in the same manner and even states: "The Holy Prophet asked `All to delete the words: "Allah's Messenger'." but adds, quoting narration of Al-Bukhari, that some have taken this as a miracle carried out by the Prophet (SA). It, however, mentions afterward:
"Some have said that this narration is not acceptable by some knowledgeable persons. It actually implies that the Prophet ordered someone to write and that he did not write it himself."
"Abul-Walid Baji Maliki from Spain, who intended to rely on the apparent meaning of Al-Bukhari's statement was seriously refuted by the Spanish scholars." 
However, Ibn Hisham's "Sirah" does not include such a statement and it is not clear as why did Dr `Abd al-Latif ascribe this to Ibn Hisham.' We have already mentioned that from the historical point of view, what is inferred from most narrations, is that `Ali (AS) wrote all the written material. That the Prophet (SA) wrote, despite his inability to write, can only be concluded from Al-Tabari's and Ibn Al-Athir's statements.
At the most this can be implied that the Prophet (SA) wrote once or more during the prophetic period, whereas, the issue under discussion concerns the period before his prophethood.
. Sahih al-Bukhari, vol 1, p 25.
. Ibn Hisham, S'irah, vol 1, p 601.
. Bihar al-Anwar, old edition, vol 6, p 575.
. Muhammad ibn 'Umar al-Waqidi, Al-Maghazi, vol 1, p 13.
. Al-Sirah al-Halabiyyah, vol 3, p 24.