The Application to Register Permanent Residence or Adjust Status form I-485 is available to download online for free at USCIS.gov, according to the U.S. Citizenship and Immigration Services. Click on the Green Card link located at the top of the home page, and select Green-Card Based Forms.
Locate the proper form, and click on the link. Form I-485 Supplements A, C and E are also available from the results page, notes the USCIS. Other green-card based forms available online include Application to Replace Permanent Resident Card form I-90 and Petition to Remove Conditions on Residence form I-751, among others.
Forms are also available by mail, advises the USCIS. From the Forms page of USCIS.gov, click on the By Mail link under the heading of USCIS Forms are Free. Follow the prompts to order the correct forms. Call 800-870-3676 to order forms by telephone, as of 2015.