Add documentation to TL install

It is possible to add documentation files to already installed packages issuing the following commands in any terminal (both commands may need root privileges depending on how you installed Tex Live in the first place and the second is UNIX only):

tlmgr option docfiles 1

sets the docfiles option to 1, i.e. from now on tlmgr will download and install documentation files every time a new package is installed. If during the installation process of TeX Live the user chooses not to install docs, this option is automatically set to 0, so you need to manually change its value.

Then issue:

tlmgr install --reinstall $(tlmgr list --only-installed | sed -e 's/^i //' -e 's/:.*$//') 

the above command reinstalls all packages listed by tlmgr list --only-installed, i.e. all already installed packages. The sed part is used to remove everything except the package name from the list generated by tlmgr list --only-installed. As an example, before the sed part the first line of the list looks like:

i 12many: Generalising mathematical index sets.

while after the sed treatment it looks like:

12many

For more info see the tlmgr and sed docs. Credit goes to Norbert Preining, see this thread on comp.tex.live

For the record, if you're using the TeXLive Utility GUI, you can also solve this issue by selecting the Configure > Configure Documentation..., checking the box labeled "Install documentation when updating", and confirming by clicking the Install now button.

(I just ran into this issue after installing BasicTeX and the TeXLive Utility GUI on my Mac, by runnning brew cask install basictex tex-live-utility.)