To reiterate what the others have said, you will want to install ADS on a separate instance, as dual-stack is not supported anymore except for a few exceptions (e.g., Solution Manager).
That gives you some freedom, however. You don't have to exactly match your ADS version to your ECC version, but your ADS version should be at least as high as your ECC version. It can be higher.
So, if you're running ECC 6.0 without enhancement packs, that means you need to install a NetWeaver AS Java system of at least 7.00. 7.01 or 7.02 should also work.
By the way, there is a forum area on SDN that might be better for ADS questions: SAP Interactive Forms by Adobe.
Best regards,
Matt