If you are looking for GATT trade documents, you might want to start with the GATT Digital Library, a digital library of over 30,000 public documents published between 1947 and 1994. The library is a shared project of Stanford University Libraries & Academic Information Resources (SULAIR) and the WTO.
“At present this site provides access to over 30,000 public documents and 200 publications of the General Agreement on Tariffs and Trade (GATT). The public documents include reports, studies, and meeting records covering a broad range of topics related to international trade in the post-war period. Each document bears a unique symbol number and the entire collection is searchable by a range of fields including symbol, date, keyword in title, keyword in title, and organization name. Subject indexing is not currently available, but project staff are collaborating with World Trade Organization (WTO) staff to identify the requirements for subject access to the collection.”