Is the post-traumatic stress disorder limited to soldiers?

Not limited. Ptsd can occur from any kind of trauma. The severity of the trauma and duration of exposure seem to play a role in who develop ptsd. Victims of rape and other crimes may develop ptsd.
No. The fact that there are so many veterans with this disease, sometimes gives people the idea that it is a military disorder. What is necessary is that that their is a trauma or traumas that are horrific or life threatening. There are many civilian who suffer from ptsd.