Merge svg files into PDF
Based on nohillside's answer and Matthieu Riegler's answer, this is my solution:

cd /
for i in /path/to/folder/*.svgz
    /Applications/Inkscape.app/Contents/Resources/bin/inkscape $i --export-pdf $i.pdf
end
cd /path/to/folder
launchctl limit maxfiles 10240 10240
ulimit -n 10240
pdfunite *.pdf book.pdf