Thanks, Gandalf!
Actually, my sig links don't link to the manual threads. The 3.21 versions of the manuals came with the 3.21 patch, which replaces the oiriginal modding.pdf and mapedit.pdf files in the Dom3/docs folder, but prior to that the 3.20 patch contained only the 3.18 manuals for the Windows version and the 3.20b patch for Linux didn't have any updated manuals. The 3.20 manuals were thus attached
here, but they are obsolete by now.