In my experience with AI learning models, there is one defined amount of training process to 'train' the algorithm. Some models depending on complexity will work with a little amount of training such as the one PDF file. It will greatly depend on the complexity you are looking for. Such as if you are trying to determine specific features, or tell the difference between one face or another. The model will work more effectively with more training data involved. If you are just looking for a face than this one PDF file may be sufficient. The answer is not a straight forward yes or no without further details into what type of data you are looking for as a differental identifier for each face.