Like others, I wanted to install the help files for LibreOffice, but found no quick and easy way of doing this. Even extracting the files, using 7-Zip, leaves some files with the wrong names and wrong locations. So, to get past this, I wrote a portable application, which I call "LibreOffice Portable Help Installer". All you need to do is the following:
(1) Download the "LibreOffice Help For Offline Use" installer from the non-portable LibreOffice site.
(2) Once you have this file, all you have to do is select the installer file, select the LibreOffice Portable installation location, and "LibreOffice Portable Help Installer" will do the rest.
Once finished, you should be able to open LibreOffice and use the Help system offline.
You may ask what languages does it support? The instructions are in English, but based on the few Offline help installers I downloaded and tested, you should be able to install any Offline help file in any language using this application. I can't say 100% if all will work, just that the couple I tested worked. The scheme seems to be the same for the few language file helps that I downloaded and tested. That means, if the rest have the same layout, that it should be able to extract and install those as well; although, you will have to install them one at a time, since this application doesn't have a batch installation.
I hope you will find this application useful. You can download it here: