Two additional Adlum documents can be found in the James McHenry papers: an official War Department letter (LS) from April 1, 1799, and a field officer circular (LS) from July 13, 1799.
The Clements Library also holds a number of books and one map by John Adlum:
Adlum, John. Adlum on making wine. 1826.
Adlum, John. A memoir of the cultivation of the vine in America, and the best mode of making wine. 1823, 1828.
Adlum, John. Memoirs of the life of John Adlum in the Revolutionary War. Edited by Howard H. Peckham. 1968.
Adlum, John, and John Wallis. A map exhibiting a general view of the roads and inland navigation of Pennsylvania, and part of the adjacent states. 1791.
The Pennsylvania State Archives also has a collection of John Adlum papers, 1794-1836.