I am fairly certain the upper limit of the raw text counter (for all of them) is 32MB. So, if you were to strip the file of all images and markup, the size can only reach 32MB before it complains. What does that mean? Well, I've seen Word files that surpass 3 million words and the page counter has rolled over (> 9 999 pages).
Now, the maximum size of the file (text, images, tables, markup included) depends on the file system you are using. FAT32 = 2GB, NTFS = 4TB.