[Checkpoint] 3.1.2 Language of Parts: The human language of each passage or phrase in the content can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text. (Level AA) [Comments] 
PDF provides support for language identification for parts of documents. Test results: Test id 17 (Document with English primary language which includes Spanish phrases)