Sure it is not a big problem to modify the file name and, actually, is what I did...
The problem is that I have lost the bookmarks: since it is a reference book and I bookmarked all the chapters, my little work is lost...
Moreover, it can happen again, by mistake, on other files, even if in the future I will be more carefull.
Finally, changing the name breaks the criterion I used to name files in my e-library (but this is a problem just for my insane mind...
)