Merge pdfs
Using Ghostscript
Ghostscript has a feature to merge multiple pdf files into one. Although ImageMagick also has this feature, I prefer this one, as it doesn’t rasterize and scales down the pdf files.
gs -dNOPAUSE -sDEVICE=pdfwrite \
-sOUTPUTFILE=output.pdf \
-dBATCH 1.pdf 2.pdf