Rupali,
As far as I know permanent residency status gives you all the privileges & duties of a Canadian citizen except voting rights. Normally a person allowed in Canada as emigrant has passed a medical examination before being permitted to enter the country. So you must have done that?
There are probably limits on how long you can stay out of Canada without loosing your status of permanent resident & must reaply for renewal of the card of permanent resident (which I am almost sure does not require a new medical examination).
If your employer is not giving you enough info on this subject you should contact any Canadian consulate.
You can also search into this web site:
www.cic.gc.ca.
The toll free number (probably valid in Canada only) is: 1-800-255-4541
or FAX: 1-888-576-8502