In the "Legislative Information" page launched with the NDL website renewal in February 2012, the Research and Reference Bureau has been providing articles from their publications―"Issue Brief," "Reference," "Foreign Legislation" and others―as PDF files.
Up to now, these articles were listed according to the posted title and the posted date. From September 4th, articles issued since 2010 ("Research Material Series" articles since 2012) can be listed by theme / country and region. With this reform, you can find the article of your interest more easily than before.
This "Legislative Information" page also provides other helpful information, such as the Full-text Database System for the Minutes of the Diet and useful links to other sources of information.