If I roll three "surge" and I have an ability that says "use one surge for +1 attack" can I use all three surge to add 3 more damage? Or do I have to use only one surge for the +1 attack and have to use the remaining surge for other things (such as remove strain etc)

Each surge ability can be triggered only once per attack. So you can use 1 on the +1 damage, and 2 on any other abilities that cost surge or recover 1 strain.

However if you have more than one surge ability like that you can use it multiple times. In example Jyn can learn to use surge abilities of any of her pistols. So she might have 2 pistols with the same surge ability and this allows you to use it twice. Another example is the Rebel Saboteur which has the ability to use the same surge ability up to 2 times per roll.

However if you have more than one surge ability like that you can use it multiple times. In example Jyn can learn to use surge abilities of any of her pistols. So she might have 2 pistols with the same surge ability and this allows you to use it twice. Another example is the Rebel Saboteur which has the ability to use the same surge ability up to 2 times per roll.

Well, not quite. The rule on weapons states: Abilities on a weapon cannot be used while resolving an attack with a different weapon.

So, if you are attacking with Weapon A, you can't use the surge abilities on Weapon B.

Unless you're Jyn with the relevant XP upgrade.