When moving all the pdf files in a particular folder to a newly-created sub-folder, about 90% of them lost their pdf extensions!
I have therefore had to add the missing extensions to each of the file names one by one!
For some reason, when I tried to restore the files to the original folder, it would not let me restore them all at once! It would only let me do it one by one, which was slower than manually adding the pdf extension to each file in the new folder.
Is this due to some sort of bug?