I’ve tried to install the Portuguese dictionaries on Open Office using the Wizard->Install dictionaries.
Due to permission issues I was unable to install it and didn’t want to mess around with permissions our sudo.
So to install:
Download the dictionaries from here: http://ftp.services.openoffice.org/pub/OpenOffice.org/contrib/dictionaries/pt_PT.zip
Unzip it to your work directory
Sudo to directory /usr/share/myspell/dicts.
Copy the files pt_PT.* from where you unziped them to this folder.
Edit the dictionary.lst file and add the line:
DICT pt PT pt_PT
That’s it. You now have the PT language installed and can go to Options->Language and set the default language to Portuguese.