A pre-industrial society was one that had not yet developed machines to aid in labor and mass production of goods.
The Akaali were considered a pre-industrial society during the mid-22nd century. Upon discovering the planet in 2151, it was determined from orbit by the crew of the Enterprise NX-01 to be of said status from the planet's lack of EM transmissions. First contact with this type of civilization was strongly discouraged on account of the risk of cultural contamination. After reviewing the notes of the Akaali Riaan, Doctor Phlox was impressed by her methods, which while they were unrefined, her forensic techniques were far more sophisticated than he would have expected from a pre-industrial society. (ENT: "Civilization")
Two pre-industrial societies known to the Federation during the late 24th century included the Barkonians of Barkon IV and the humanoids native to Veridian IV. (TNG: "Thine Own Self"; Star Trek Generations)
In 2373, the USS Voyager encountered the Takarian homeworld in the Delta Quadrant, they determined that the native Takarians, based on a metallurgic analysis from orbit, to be a pre-industrial civilization with a Bronze Age level of technology. (VOY: "False Profits") Similarly, the Mintakans were also a Bronze Age level pre-industrial society. (TNG: "Who Watches The Watchers")