There are specific saddles designed for the Paso Fino ride.  They are all based on the old Mclellan cavalry saddle, and are often called modified Mclellans.  These come in all different styles, including ones with horns.  There are also Colombian training saddles available.  There are two Paso Fino Handbooks here on ebay, available to help you decide what you need before you buy anything.

     The reasons for using one of theses types of saddles over others of Western or English design are varied. 

• Correct Seat.  These saddles sit you back on your pockets and deep in the saddle.  This position helps you to arch your back in the correct manner for the best seat, rather than what you are used to with the English or Western seat.  Being loose in the small of your back is critical to your ride. It is not impossible to get the correct seat with another type of saddle, however, these saddles really facilitate your correct posture.
  
• Contact with the Horse.  Contact with your Paso Fino is so important to getting the best ride than you can.  Some saddles sit too high off the horse and you get very little contact with the horse.  Pasos are very weight sensitive and will respond to your subtle cues.  If you are sitting too far off the horse, then you won't know what you are telling your horse to do.
  
• Three Quarter Rigging.  A 3/4 rigging attaches at the front and the back of the saddle to a center cinch.  This option secures the saddle to the horse more securely than any other type of rigging.

     The biggest thing that you have to remember is that Paso Finos are generally smaller horses, and can't ride the big, huge Western saddles with the long box skirts.  Those saddles do not fit the Paso back and interfere with the proper gait.  There is a lot of movement going on in the shoulder and hip.  If you really want to ride a Western saddle, then get one with short rounded skirts like you would find in a Western saddle designed for an Arabian. 

     There are individual exceptions, of course, to all of the above.  It all depends on the horse that you buy.  I would always recommend getting the horse before you buy a saddle.  Fit your saddle to your horse and to yourself, rather than trying to fit the horse to the saddle that you already have.  Remember, you have to fit your shoes to your feet, not the other way around.  Horses are the same.  Fit the saddle to the horse.

     Buying a saddle is strictly a personal preference and you have a big variety here, and can go as cheap or as expensive as you like or can afford.   Don't worry, you don't need to impress anyone except your horse with your concern for his comfort.  So ride what FITS.