Authorities say the 67 protestors were pardoned to promote calm and national reconciliation.
Deby also issued pardons for 11 people accused of taking part in an attempted coup, according to two decrees dated Wednesday.
Deby had previously pardoned 259 out of 262 young people who had been jailed after the protests, as well as 380 Chadian rebels who had separately been sentenced to life.
More than 600 young people, of whom at least 80 were minors, were rounded up and hauled to a notorious desert prison, Koro Toro, more than 600 kilometers from the capital, where they were later put on trial.
In one of Wednesday's decrees, Deby pardoned Baradine Berdei Targuio, the head of the Chadian Organization for Human Rights (OTDH) and 10 army officers.
They had been arrested in December on charges of fomenting a coup, and were sentenced in mid-May to 20 years in jail.
Seventy-seven people were sentenced earlier this month for terms ranging up to five years on charges of taking part in an 'insurrectional movement" or an "unauthorized gathering" in demonstrations against the ruling junta.
Deby was proclaimed head of state by the army in April 2021 after the death of his father, Idriss Deby Itno, who had been killed during anti-rebel operations after 30 years of iron-fisted rule.
He immediately promised to restore civilian rule after an 18-month transitional period.
But as that deadline neared, the period was extended by a further two years, following a so-called national dialogue widely boycotted by the opposition and armed rebel groups.
The October 20 demonstrations aimed at marking the deadline of the initial 18-month period, but turned into bloodshed as police and troops opened fire.
In the capital N'Djamena, 73 people were killed, according to the authorities.
The toll is contested by the opposition and civil groups, who say hundreds died, either on that day or in the ensuing crackdown, and others were tortured.