First this lists all file names (directories), extracts those in the /mnt or /home directories, extracts those with .odt or .pdf or .doc extensions, sorts them and eliminates duplicates, then finally removes the first letter of the results.
lsof -Fn | grep -E '/mnt|/home' | grep -E '.odt|.pdf|.doc' | sort | uniq | sed 's/^.\{1\}//'