So I'm curious: what tools did people use to produce those documents?
What was available at the time? Some of the first were done with a typewriter ;-). That said, a lot of the early ones (1960-thru late 70s) were done using one of the different flavors of the runoff schemes, with the PDP-10 family being pretty popular since many of the Arpa supplied systems were based on PDP6/10s. The output, as you see, was formatted ASCII printer listings. Once Unix hit the scene, particularly with Vaxen, nroff took the lead, but since other than CMU/Stanford/MIT, XGPs (or later Dovers) were rare. Using a plotter (a.k.a. vcat and family) troff starts to take off it some places beyond folks with an XGP (like UCB). By the time of the many different JAWS, and the Apple Laserwriter and eventually different HP printers, the nroff/troff family was very much the norm, with some Tex/LaTex at some point. MS-Word does not start to show up until about 15-20 years into the process.
As you noted, Bakul has a pointer to the current set of tools; but you asked in the past tense; so I'm assuming you mean, how did the first 1-2K or so get created.