All pilgrims desiring a Compostela MUST present themselves in person at the Pilgrim Office to request the Compostela. They must present the required evidence, in the form of a properly stamped and dated credencial that establishes they walked AT LEAST the final 100 km of any accepted route into Santiago.
By way of an example, in 2016, I started from Madrid, making made it as far as Sarria before unrelenting pain in my hips, knees, and ankles compelled me to stop my Camino about 118 km shy of the Cathedral at Santiago. I did not claim a Compostela for that pilgrimage.
The sole exception is that you can dedicate YOUR compostela to another person who is either deceased or whose physical condition means they will never accomplish a Camino. You are considered to have done your Camino 'in place of' the other person. The latin term "In Vicare Pro" along with the other person's name (given name in Latin) is written at the bottom of YOUR compostela. You request this annotation when you arrive at the processing counter.
Hope this helps.
