Use this custom Google search box to search for federal, provincial and municipal government publications for Canada. After you run your initial search, there will be tabs for the separate levels of government to help you narrow down your results.
For other countries, look for government sites similar to those in Canada. If you cannot find a site that allows you to search for publications across the government, most will have departments responsible for tourism, natural resources, the environment, economic development, etc. Each of those will often have publications available on their websites.
Also, try the Advanced Search in Google (under Settings) and specify .gov as the "site or domain:". This will limit your results to those from government sites only.