Yesterday I stumbled upon a part of Wikipedia which is called Wikipedia Commons. Maybe known to you, but new to me.
I'm just in the phase of discovering it, there sure is much-much more to be discovered here. But this is what I came across just now:
Acknowledgement of service obligation sgned by Elvis Presley on March 24, 1958, to indicate that he understands that his total service obligation (both active and reserve) is 6 years:

Message from U.S. Army, Public Information Division, releasing information about Private Elvis Presley's basic and advanced training, with approximate date of assignment to 3rd Armored Division in Germany - May 28, 1958:

Letter from Lt Colonel Verne L. Bowers to the Honorable Frank Kowalski, Member of Congress, explaining that Elvis Presley will not be given an early release for "good behavior". Sept 8, 1959:

Source: http://commons.wikimedia.org
Please, help searching and share your findings

.