This post is aimed at investors in Canadian stocks, so for the 80% of you that ignore this market, you can skip now.
You don't see who the significant shareholders are (and how their holdings have changed) when you look up the filings of Canadian issuers on Sedar. That's not because insiders are not required to report their holdings or changes to their holdings. It's because there is a separate reporting system just for this purpose.
On SEDI, you can find information relating to insider transactions by issuer or by insider, making it a rather powerful tool. Insiders include (by definition, through National Instrument 55-104) shareholders who own more than 10% of a security.
So if you want to know if a senior manager has been buying up shares, or who the significant shareholders are of a company you own, it's easy to find out.