Yes, to a very high sense it is totally compatible. Only at the most advanced usage with advanced use of macros might there be a problem.
The same is true of OpenOffice but Libre Office has one advantage over OpenOffice in that it can both read and write .docx files – the default format for Microsoft Office. Open Office can only read .docx, but writes out in a slightly different format.
As I recall, LibreOffice can also read .PDF files. We covered this in a Computer Group meeting and without checking I can’t remember that for a fact off the top of my head.

