They have agreed on many documents throughout their history. Both are signatories the UN Declaration of Human Rights. Both ratified the Treaty of Maastricht and both were Allies of the British in the Napoleonic Wars (and agreed to Articles of Alliance).
The most famous document that these two parties negotiated and agreed on was the Treaty of Tordesillas which split the world into areas that Spain could colonize and those that Portugal could colonize, without fear from the other party infringing on "their territories".
(1494)
1494
1494
Spain is known as Spain and Portugal as Portugal.
Portugal is west of Spain, between Spain and the Atlantic Ocean.
South America back in the 15th century
Portugal is bounded by the Atlantic Ocean and by Spain.
Portugal is west of Spain.
Spain and Portugal both sponsored him
Spain is the only country that borders Portugal.
Portugal is west of Spain.
Spain wished to compete with Portugal for trade. (Apex)