Dear Ms. King,
Thank you for posting your request on History Hub!
To find his original Petition for Naturalization Form, it is important to know when he submitted his petition. For pre-1906 naturalizations, contact the State Archives for the state where the naturalization occurred to request a search of state, county, and local courts records. After 1906, the courts forwarded copies of naturalizations to the Immigration and Naturalization Service (INS). Naturalizations from Federal Courts are held in NARA's regional facilities for the Federal courts for their area.
To print it out from Ancestry, there may be a fee associated with obtaining a copy. However, you may view these records online at one of NARA's facilities for free via a NARA PC. For the nearest NARA location, please consult our web page at https://www.archives.gov/locations/. Also, some of the images from Ancestry are available for free on Family Search at https://www.familysearch.org/en/.
We hope this is helpful. Best of luck with your family research!