When I export pdf file from ipad to dropbox, then copy the file from dropbox to pc, it's fine. But if I copy the same pdf file to the external HD, it says there's not enough memory to complete the operation, basically can't copy pdf to external hd if it went through dropbox. why is that?
P.S. I tried to use Box and Google Drive instead to copy the same file, they work fine. So dropbox must have done something to the pdf file.