The Austrians had 60 divisions in the theater as of Vittorio Veneto - I don't think adding additional men would have been too productive anyways. Honestly, I get the sense that they and the Bulgarians should have been able to hold out longer than they did - the numbers were there, but after the failure of the Spring Offensive, morale simply wasn't.
Morale and more importantly supply, numbers can be deceiving
In theory the strength of the opposed armies was more or less the same (60 divisions on each side) and both had felt the impact of malaria and Spanish flu when the offensive of Vittorio Veneto started on 23 October 1918. In practice the Entente had a clear superiority in artillery and supplies, and - most importantly - morale: the Italian troops had been retrained and reorganized over the winter, they had full confidence in the new CiC (Armando Diaz had refused to immediately counter-attack after repulsing the last A-H assault at the end of June and spent the next three months preparing in detail the decisive offensive) and they knew this would be the last effort.
On the other side, morale was low and the KuK army was not in a good state: when Boroevic, the last Austrian CiC, ordered a counter-attack against the two Italian bridgeheads on the eastern bank of the Piave the troops refused to obey. Even more tellingly, the front of Monte Grappa (which had not moved much during the entire war) was broken by 30 October.
Ludendorff wrote that In Vittorio Veneto, Austria did not lose a battle, but lose the war and itself, dragging Germany in its fall. Without the destructive battle of Vittorio Veneto, we would have been able, in a military union with the Austro-Hungarian monarchy, to continue the desperate resistance through the whole winter, in order to obtain a less harsh peace, because the Allies were very fatigued.