Presidential documents are freely available from multiple places online. Below is a selection of these websites.
Compilation of Presidential Documents govinfo
Includes the Weekly Compilation of Presidential Documents and the Daily Compilation of Presidential Documents. Coverage begins with 1992.
Public Papers of the Presidents of the United States govinfo
Public Papers of the Presidents National Archives
For additional information about the Presidential Papers at the National Archives, see National Archives Announces a New Model for the Preservation and Accessibility of Presidential Records and The Obama Foundation and NARA Announce New Details on Obama Presidential Center Structure and Operations.
Digital Collections: American History Library of Congress
Includes papers and essays from or about select U.S. Presidents.
Presidential Collections include:
The Papers of the Presidents The Avalon Project, Yale Law School
End of Term Archive
Captures and saves U.S. Government websites at the end of presidential administrations. Contains federal government websites (.gov, .mil, etc) in the Legislative, Executive, or Judicial branches of the government. Websites that were at risk of changing (i.e., whitehouse.gov) or disappearing altogether during government transitions were captured. Includes 2008-2009, 2012-2013, and 2016-2017 presidential transitions.
Executive Orders and Other Presidential Documents: Sources and Explanations Law Librarians' Society of Washington, DC
Briefly explains and links to major sources for materials including Presidential directives, proclamations, signing statements, executive orders, memoranda, and other documents.