The MacBook Pro 13” 2.7GHz dual-core Intel Core i7 can be maxed out to accept up to 16GB of ram and I suggest you do so. RAM is cheap and you can now buy 16GB ram for this MacBook Pro model for under $100.
If 16GB is too much ram, or too much money then you might want to consider using just 8GB but the price difference between 8GB and 16Gb ram isn’t really all that much and you will get much more value with maxing out the 13 inch MacBook Pro vs just using 8GB.
Where to Buy RAM for the MacBook Pro 13” 2.7GHz dual-core Intel Core i7
There’s many places to buy ram, but if you’re shopping for Mac Memory I suggest you stick to these memory brands: