The list comes first, the French second
Most of the difficulty on this route arrives before a word is translated. An office in Gabon writes its requirements in French, using the names its own system gives to things, and you hold a drawer of British papers whose names do not line up one for one. Matching the two lists is the real first task, and it is done with the documents in front of you rather than with a dictionary.
The language Gabon requires
A certified translation into French in Leicester is required for documents that will be used in Gabon, so every British page in your bundle needs a French version beside it. The English is not withdrawn or altered; it stays as issued and the French is produced alongside. What decides the size of the job is how many British papers the checklist actually calls for.
The signature this route needs
The French must carry a sworn translator's signature, the traducteur assermenté of French-language practice, dated and tied to the document it accompanies. That narrows who may take the work on, which in turn shapes the timetable more than the length of any single page does. It also means the person who chose each French word is the person answering for the choice.
Per-page cost and turnaround
An official French translation in Leicester is £25 a page, delivered in 2–4 business days or in 24–48 hours on the express route. Because the price follows the page count, the checklist is also your budget: a line you misread into two documents costs twice. Reading it carefully at the start is the cheapest work anybody does on this whole errand.