Google and the USPTO have entered into an agreement to make the following USPTO products free to the public:
Patents (grants, applications, assignments, classification information, and maintenance fee events)
Trademarks (grants, applications, assignments, and TTAB proceedings)
Google is hosting this data unchanged, except for repackaging into zip files.
Here are instruction on how to do this from Espacenet using zotero. Not all databases let you download to Bibliographic Management software.