Suarez, voted player of the tournament, put Uruguay ahead in the eighth minute of the final at the Monumental when his low, left-footed shot from the right beat the diving Justo Villar and went in off the far post.
Forlan, the 2010 World Cup's best player, made it 2-0 three minutes before half-time when he ran onto a ball from midfielder Egidio Arevalo Rios and blasted left-footed past Villar from the edge of the box.
In the last minute, Forlan made sure of the title with his second goal at the end of a fine counter-attacking move, steering the ball past Villar and in off the post.
Uruguay now have one more title than hosts Argentina, whom they upset on penalties in the quarter-finals, at the end of a fine 12 months following their fourth place at the World Cup.
Outgoing champions Brazil, also eliminated in the quarter-finals on penalties by Paraguay, have eight titles.
Twice champions Paraguay finished the tournament without a victory having reached the final with five draws and two penalty shootout wins.
Suarez scored four goals in the tournament, one less than top scorer Paolo Guerrero whose hat-trick helped Peru beat Venezuela 4-1 for third place in La Plata on Saturday.
Forlan, who won a Uruguayan record 82nd cap, ended a year without scoring for his country with his two goals and equalled the national record of 31 held by Hector Scarone.
Uruguay laid siege to the Paraguay goal from the start, winning four corners in the opening eight minutes with the defence clearing one chance following a header from Diego Lugano parried by Villar.
Paraguay created their first chance on the quarter hour when midfielder Enrique Vera's right cross to the far post was a bit too long and striker Nelson Haedo Valdez's effort went wide.
Past the half hour, Forlan had his first chance but Villar saved and minutes later Suarez hit the side-netting from a tight angle on the right.
Haedo Valdez volleyed Paraguay's best chance onto the bar from midfielder Nestor Ortigoza's chip forward early in the second half.
Ten minutes later, Paraguay right back Ivan Piris took a ball out wide and crossed low with keeper Fernando Muslera diving at centre back Paulo da Silva's feet to save.
Then Villar made a good save from midfielder Sebastian Eguiren after taking a pass from fellow substitute Edinson Cavani.