you need permission from the owner of the photograph to publish it if you are making money, if you are not making money and it is in a protected document, then it is allowed under the 'fair use' policy.

Model Releases
Model Releases are essential throughout the world, especially when a photograph of a recognisable person, of any age is used in advertising. Even if the face is not visible but the person is capable of being identified then a model release is required. For example:
Parts of the body can be identified due to markings such as tattoos, birth marks etc.
A silhouette of a person if it can be recognised by its location
People in crowd shots, if that person is considered to be the focus of the shot.