Apple - I downloaded a shell executable and man pages from a source I trust. Where should I put them?

The binary file goes in /usr/local/bin. Each man page goes in the folder usr/local/share/man/manN where N is the number at the end of the man page file name. For example, gdisk.8 should appear in the folder /usr/local/share/man/man8. When finished adding all man pages, you should run the command

/usr/libexec/makewhatis /usr/local/share/man

to update the whatis database stored in the text file /usr/local/share/man/whatis. This whatis text file is used by the whatis and apropos commands.

/usr/local in general is the place to install user-provided unix-like software.

• For the binaries, see Where should shell tools be installed? or Where should shell tools be installed? which both point to /usr/local/bin.
• For man pages use /usr/local/share/man/manN (with N being the chapter, usually 1 or 8 for commands) and make sure /usr/local/share/man is in /etc/manpaths (or added as an additional entry in a specific file in /etc/manpaths.d).