In total the number of treaties was 5, including the Treaty of Versailles with Germany, and one treaty each with Austria, Hungary, Bulgaria, and the Ottoman Empire.
The writing of these treaties proved to be difficult. Secret wartime treaties promised things that conflicted with the ideas of the writers. In fact, the authors of the peace treaties often disagreed among themselves. Before the treaty was drawn up, Soviets already were inciting revolutions in Germany and the former Hapsburg lands. And the authors were more interested in specific gains for their own countries.
The majority of those invited to the peace conference were the major Allied nations and a few others, including Nicaragua, Liberia, and Siam, who had severed diplomatic relations with the Central Powers. Also present were representatives from the colonial territories. Those representatives of nations allied with Germany were not invited until it was time to sign the treaties. Due to revolutions in its country, Russia was not present.
Most of the decisions were made by the Big Three: Georges Clemenceau (Fr.), whose aims were to weaken Germany and gain territories; David Lloyd George (G.B.), who played the role of the mediator between Clemenceau and the other man; Woodrow Wilson, who was the visionary of the group, wanting everything to be decided rightly and justly, he felt that his 14 Points was the idea solution for peace.
However, the Treaty of Versailles was not written to the 14 Points, but to claim revenge on the Germans. Clemenceau wanted to dismember Germany with no regard for ethnic, economic, or other considerations. Wilson and Lloyd George were able to hold back his most extreme measures, though.
Because of their extremely different views of how the treaty should be, the final one satisfied none of them: Clemenceau thought it too moderate, too easy on the Germans, Lloyd George felt it was too harsh, and Wilson believed it had too many flaws.
Had the peace treaty been less harsh on Germany, drawn borders on ethnic lines, and generally followed Wilson's 14 Points, the new Europe might have been more stable, it may have been possible for the world not to have been plunged into World War II.