The way CIC reviews it is that you must be posted to a full time position outside Canada in order for your days outside to count and who you are working for is also an issue. If immigration feels that you have started your company for the prime purpose of being able to stay outside Canada and still meet the RO, they would not approve.
You wouldn't be asked for an employment records to renew your PR card. You need to list your travels and if they feel that something doesn't match and want more proof that you have been in Canada when you said you were, they will ask for more proof. For an employed person, that would be employment records but if you are self employed, you will have to look for something else, cell phone bills or bank records might show where you were. You could also get a print out of your health records to see when you have visited the doctor because those will prove that you were in Canada at least on those days.