Linux: Compressing all .pdf files recursively (.tar)
Solution 1:
Try this: find -iname '*.pdf' -print0 | xargs -0 tar -cf docs.tar
Solution 2:
PDF files are binary files and probably won't compress much. tar doesn't compress anyway, without the -z option, and it would leave the uncompressed PDF files in place.
But if you want to try compressing PDF files, you could use
find . -iname '*.pdf' -exec gzip {} \;
This will compress all PDF files (and only PDF files) in folders below the current directory.
Each filename.pdf will be replaced by filename.pdf.gz