I recently downloaded the free substitute for Microsoft Office named LibreOffice. This is an open source program from many of the same developers of OpenOffice. Like OpenOffice, it is available for Windows, Macintosh, and Linux platforms. http://www.libreoffice.org/
It seems to open all MS Office files seamlessly and can create or edit those files with no problems. Previously, with OpenOffice, I had found problems with positioning graphics when switching between Word and OpenOffice. This could be a serious problem if you created or edited a file, saved in in the .doc format and another person opened it with Word and found the formatting had become scrambled.
This glitch seems to have disappeared with LibreOffice. As a test, I opened my fitness book, that has many photos and other graphics in it. I made a few changes, saved it in the .doc format, then opened it with Word. Hurray! No problems, everything was where it belonged, including text boxes, pictures and clip art.
On the Macintosh, there is a feature in the printing module that permits saving as a.pdf file. This is handy but the files are often larger than useful for sending via emails. In LibreOffice, that feature is in the File menu and the resulting .pdf document is of high quality and of a reasonable file size. Previously, I had to go through extra steps to reduce the file size. They were not extensive but no steps is better.
I also tried PowerPoint files and they opened and displayed with no problem, as did Excel .xml files. I didn't create any of these, as I never make PowerPoint presentations now, preferring videos instead. When I made some changes in the .xml files and then opened them in Excel, there were no problems I could detect.
In conclusion, LibreOffice seems to be an excellent replacement for MS Office. It's free, it works, is compatible with those using office, and translates document into other formats with no problems.