The Tourist Office is on the first floor of a modern office block tucked into the left hand side of the Plaza España (if facing the direction of the port). They provide pilgrims with:
Credencial, Sello, Map out the route (showing 2 alternatives) from the city to the outskirts: A copy of the Xunta Guide in English: A schematic of the distances and elevations on the route (which isn’t terribly accurate!): A Gallego phrasebook (which is perhaps too heavy to carry): And…they have good toilets if setting off immediately from there!
NB: It is important that you obtain a sello in Ferrol to demonstrate to the Pilgrims’ Office in Santiago that you have walked more than 100 kms in order to qualify for the Compostela. There is no requirement for that sello to be from the Tourist Office and you may have your Credencial stamped in your hostal etc.