If something is obtainable, you can get it. The word does not say you must get it, or that getting it is easy — only that getting it is possible. A book still in the shops is obtainable; a ticket that sold out last night is not. People use this word more in notices, forms, and careful writing than in chat with friends. A friend would usually say “you can get it” or “it’s available.” Shops, libraries, and offices like the pattern “obtainable from…”: obtainable from the school office, freely obtainable online. You can also talk about information, help, or a result as obtainable, meaning it is within reach if you try. Though actually, when people say something is “easily obtainable,” they are often making a quiet point about fairness or luck — anyone can get it, so there is no special excuse, or anyone can get it, so it is not rare or precious. The opposite, unobtainable, is common too, and it can sound a little heavy, as if the thing is out of reach on purpose.