Again, I will note that you are now outside the normal type application and thus would benefit from an experienced Canadian immigration attorney.
If it has been five years since you completed any sentence associated with this conviction, you may be eligible for rehabilitation. One reason it is difficult to say is that one must examine the foreign statute and determine what the corresponding Canadian criminal statute would be and what the maximum penalty would be under the Canadian statute. You may research this directly of course.
The forms for criminal rehabilitation are here: http://www.cic.gc.ca/english/information/applications/rehabil.asp. This application requires specific additional paperwork, such as court records, copies of the legal statute, etc.
Have you already submitted an application to CIC? If not, you can include the rehabilitation application with a PR application. If so, you would have revealed this conviction on your application, so they won't be surprised when you send in a rehabilitation application.
Note there is a fee of either $200 or $1000 for rehabilitation, depending upon the severity of the offence. The VO will evaluate your application and determine if you are rehabilitated. In a situation in which you have a single incident for which you completed your sentence (including parole or probation) more than five years ago and you have a clear explanation of the circumstances and you convince them that you are unlikely to offend again, then you have a good chance of success.