I fondly have paper copies of Vol I and Vol II on my shelf next to the Multics book. The PDF referred by the above seems to be only one volume, with command references not the technical papers.
You may be interested in the similar process I went through in 1997 to make a PDF of the Sixth Edition manual, including the papers: https://github.com/ericfischer/v6man/
The files for the Fourth Edition papers did not survive, only what is what is archived at ftp://minnie.tuhs.org/UnixArchive/Distributions/Research/Dennis_v4/
