/usr/lib/pd/extra/pdstring/ is in pd-pdstring 0.10.2-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/pd/extra/pdstring/LICENSE.txt
/usr/lib/pd/extra/pdstring/any2bytes-help.pd
/usr/lib/pd/extra/pdstring/any2string-help.pd
/usr/lib/pd/extra/pdstring/any2string.pd
/usr/lib/pd/extra/pdstring/any2wchars-help.pd
/usr/lib/pd/extra/pdstring/any2wchars.pd
/usr/lib/pd/extra/pdstring/bytes2any-help.pd
/usr/lib/pd/extra/pdstring/bytes2wchars-help.pd
/usr/lib/pd/extra/pdstring/pdstring-help.pd
/usr/lib/pd/extra/pdstring/pdstring-meta.pd
/usr/lib/pd/extra/pdstring/pdstring.pd_linux
/usr/lib/pd/extra/pdstring/printbytes-help.pd
/usr/lib/pd/extra/pdstring/printwchars-help.pd
/usr/lib/pd/extra/pdstring/string2any-help.pd
/usr/lib/pd/extra/pdstring/string2any.pd
/usr/lib/pd/extra/pdstring/wchars2any-help.pd
/usr/lib/pd/extra/pdstring/wchars2any.pd
/usr/lib/pd/extra/pdstring/wchars2bytes-help.pd