When sourcing a folding machine, you must prioritize folding speed (sheets per hour) and paper weight compatibility (GSM range). Ensure the machine supports the specific fold types you require, such as letter, zigzag, or double-parallel folds. For high-volume operations, look for suction-feed systems rather than friction-feed to prevent paper jams and static issues. Additionally, verify the maximum and minimum sheet sizes the equipment can handle to ensure versatility across different print jobs.