You may search a document by providing a search term in the "Advance Search" page.The "Search results" page present all documents that have the search term in their properties (i.e. Title, Reference, Keywords, Description, Related documents). Therefore, you can refine your search by clicking on one or several elements present on the right column (Source/document type etc.).
Most of the documents in the Document Register are in PDF format (download Acrobat Reader). There are also documents in Microsoft Office 2010/2007 (Office online file converters and viewers) and in compressed (.zip) format.