Which languages are EASA exams and other documents available in?
This post is an answer to the original question:


  Which is EASA official language? English or all European Union Languages?




EASA communicates in English. They facilitate the translation of regulations to all member languages, but ultimately these translations are not within their domain of responsibility.

Therefore the official language appears to be English only. 

See https://www.easa.europa.eu/the-agency/faqs/regulations:


  Implementing Rules are available in all of the national languages of the EASA Member States. How is the quality of these translations assured? Who is responsible for the translations?
  
  EASA is committed to facilitating the production of good quality translations. To ensure this and, where necessary, to improve, EASA has set up a Translation Working Group in 2008. This Working Group is made up of members of the National Aviation Authorities (NAAs), the Translation Centre of the EU Bodies (CdT), as well as EASA staff members. Also, EASA in cooperation with NAAs and CdT, is developing glossaries in the different aviation domains, such as Air Operations or Air Traffic Management, to enhance the quality of translations. The Member States also contribute to this project in order to capitalise on existing material and experience.
  
  The final responsibility for translations lies with the EU Commission. The correction of translation mistakes of the Implementing Rules follows the same formal procedure as for their adoption: 1. preparation of the proposal, 2. interservice consultation, 3. committee, 4. scrutiny of European Parliament and of European Council, and 5. adoption. For minor mistakes, the procedure may be shorter. In any case, the linguistic changes will have to be agreed by the Commission’s translation services. These linguistic services will check that no substantial change is introduced, that the term used is acceptable according to an internal translation code or that the same change is included in all linguistic versions.


And here https://www.easa.europa.eu/the-agency/faqs/recruitment:


  What language should I use in my application for a post at the Agency?
  
  Applicants may use any of the official languages of the European Union when applying for a post advertised by the Agency. However, in order to speed up the selection process and to reduce the amount of the translations needed, applicants are invited to use English. Nevertheless, applicants will not be disadvantaged in any way even if they use other official languages of the European Union. 
  
  [...]
  
  What language should I use in my application for a traineeship/study placement at the Agency?
  
  A very good knowledge of the English language is an essential requirement to do a traineeship/study placement at EASA. Applications must therefore be submitted in English. For the same reason, the documents concerning traineeships and study placements at EASA are only available in English.