find WRITE_PATH_TO_ZOTERO_DATA_DIRECTORY_HERE -name '*.pdf' | perl -p -e 's/(.*)\/(.*)\/(.*)\.(.*)/"\1\/\2\/\3.\4" "\/tmp\/ZotPad\/\3_\2.\4"/' | xargs -L 1 ln
When you have done renaming and copying the files, drag and drop the content of your temporary folder into iTunes file transfer screen.
Before you attempt this solution, you should be aware that this will not make the files between your computer and ZotPad to sync automatically. You need to repeat this process every time you change a file or add a file to Zotero, which makes this an impractical solution except for special cases where the library is known not to change over time.