Benzodiazepines such as Klonopin (clonazepam) are not generally recommended for people who have PTSD (post traumatic stress disorder). There is limited research for benzodiazepines being effective in PTSD. In addition, benzodiazepines have a potential for dependence and addiction- so this is very problematic, especially with the high occurrence of alcohol and drug abuse in people who suffer from PTSD.
If a benzodiazepine is prescribed by your doctor for PTSD, it should only be taken for a short period, until another primary treatment becomes fully effective, like with CBT (cognitive behavioral therapy), SSRIs (selective serotonin reuptake inhibitors), or SNRIs (serotonin norepinephrine reuptake inhibitors).