Well you'll get a certificate for each exam you take, regardless of which exam board you took it with. So you can keep them all together in a folder for example.
Aside from that, each separate exam board will keep a record of your results that you took with them.
If you take your exams somewhere like Tutors and Exams, when you log into your account online you can see all the exams you've taken with them, even if you took them on different years or with different exam boards.
Does that answer your question?