Haven't this been discussed in another thread?
Saudi Arabia doesn't need troops to defend itself against ISIS. They have enough military might to take care of a group like ISIS. Groups like that can only find space in countries like Iraq, Syria or Libya where government has lost control over large territory and factional fights are order of the day. This is not the case with KSA. ISIS is already on defensive and all it can do in KSA is couple of blasts or assisnations. But that would be suicidal and they would not risk taking on such powerful military of the region. They would rather try to play out Iran-KSA differences in their favour.
KSA-Pakistan relationship is much deeper than this. KSA has always stood by Pakistan and both militaries have long standing ties. This means they train together in each others countries. There are Pakistan military personnel in KSA and there are KSA military troops in Pakistan. None is defending each other. They are just training and learning together. Just like allies do. Pakistan has been heavily engaged in Counter Insurgency ops for years now. They have valuable experience in this and KSA will be very interested to gain that knowledge. If I am not wrong, Turkish Army Chief visited Swat after Operation and Turks were very interested in how PA managed to wipe clean Swat valley from terorrists. As allies to Turkey and KSA we will share that experience and provide guidance when required.
If it troubles some haters, so be it. We won't betray our friends who haven't betrayed us.