As the "FM 2-19.4" label on the top right corner indicates, this is simply a translated U.S. field manual -- FM 2-19.4 is "Brigade Combat Team Intelligence Techniques". This is far from "secret"; the Army Publishing Directorate page has it categorized as "Controlled Unclassified Information", i.e. something that isn't classified or secret, but which they don't freely distribute to the general public.
In other words -- you can't get it from the Army without an official login, but you can literally buy it on Amazon for $3.99.