EUR-Lex - http://eur-lex.europa.eu/en/index.htm  - find the document; select Bibliographic notice; details of amendments are given under the Relationship between documents heading. 

Directory of Community Legislation in Force - this gives references to amendments.
 

Encyclopaedia of European Community Law - amended legislation is either reprinted as amended or footnotes give details of amendments.*

*held at Gray's Inn, Inner Temple, Lincoln's Inn and Middle Temple Libraries 

Justis EU - retrieve the full text from the EU database and select the Amended By tab to see how it has been amended.
 

Lawtel EU - the summary document gives details of amendments.
 

Westlaw UK - find the full text in the EU database; under the Related Information options, select Modifications.