If the Portuguese special characters (like ã, é, ç ) look like strange symbols, change your media player's text encoding to UTF-8 .
In many regions (including Portugal and Brazil), the complete series is available here. You can toggle Portuguese subtitles directly in the audio/subtitle settings menu.
If you are accessing the show in the US, Portuguese options may be more limited, but it is the primary home for the series. Subtitle Database Websites
One of the largest global databases with numerous "Português (pt-PT)" and "Português (pt-BR)" options for every season.