I did a comparison using three free online PDF to Word converters using a 60 page pdf file. The best of the three was the one at this site http://convertonlinefree.com/. It was fast and it could handle this very large file.
The other two took too long to upload the files and when they did the conversion it was incomplete because there was a limit to the amount of pages for their free version.
How accurate was the conversion? I would say 100%. None of the characters were lost. All the graphics and tables of the the original file was faithfully reproduced. Editing the Word file was a breeze.
So if you are having difficulty with your conversions, try this site.