# find all file name ending with .pdf and remove them
find -name \*.pdf | xargs rm

# if file name contains spaces you should use this instead
find -name \*.pdf | xargs -I{} rm -rf '{}'

# Will show every .pdf like:
#	&toto.pdf=
#	&titi.pdf=
# -n1 => One file by one file. ( -n2 => 2 files by 2 files )
find -name \*.pdf | xargs -I{} -n1 echo '&{}='

# group words by three in a string
seq 1 10 | xargs -n3 echo