The Viola, having already assured themselves a place in the last 32 of the competition after four wins from four group games, left out their top stars for the encounter in Portugal.
The closest either side came to scoring was in the 86th minute when Fiorentina goalkeeper Gustavo Munua was forced to fully stretch to clear Manuel Vieira's stinging drive from 30 yards.
The outcome leaves Fiorentina unbeaten in the competition and still leading the pool with 13 points, one clear of FC Dnipro, who have secured second place and have already qualified for the next round.
The Italians go into their final match against Dnipro on December 12 with top spot on the line.
Winless Pacos, meanwhile, who lie at the foot of the standings, will be looking to end the competition with victory at Pandurii.
The hosts enjoyed a strong start and threatened in the 12th minute when Ruben Ribeiro surged inside the area and fired a right-footed shot that went just wide of the far post.
Bebe wasted a good chance to put Pacos ahead in the 20th minute when he struck the ball straight at Fiorentina goalkeeper Munua from a good position.
Before half-time, Nenad Tomovic blocked Tony's goal-bound attempt from outside the area as the hosts looked more dangerous.
The visitors showed more determination after the re-start and had their best chance in the 76th minute when Alberto Aquilani's powerful header from Matias Fernadez's cross was kept out by Pacos goalkeeper Antonio Filippe.
At the other end, Munua was called into action to clear Vieira's attempt from outside the area.
With four minutes remaining, Fiorentina's Marcos Alonso fired a shot just over the bar in what was the last chance of the game.