Papers a register holds
Births, marriages and deaths registered in the city are held by Southampton Register Office at 6a Bugle Street, Southampton SO14 2AJ, which issues certified copies of them on request. That is a comfortable position to be in. If a copy goes missing, gets torn or falls out of date, another one can be ordered, and the record behind it never moves.
Papers nobody will reissue
The other pile has no register behind it. A signed contract, a reference, a bank letter or a board resolution exists because somebody wrote it, and only that person or firm can produce a second one. A certified translation into Indonesian in Southampton can be made from a scan of any of them, but the sheet itself should never be risked in the post.
The language work does not care
A certified translation for Indonesia is into Indonesian, whichever pile the sheet came out of. The sworn translator reads what is in front of them and renders it, and the certificate they sign names the pages covered. Work runs at about £25 / page, so the count of sheets rather than their origin is what the invoice follows.
How long it takes
Standard work takes 3–5 business days and express work comes back within 48 hours. Those figures cover the writing and the signing only; ordering a certified copy from the register office happens beforehand and runs to its own clock. Build both into the plan, and treat any sheet nobody can reissue as irreplaceable from the outset.