Combine top halves of two PDF into one page, rotating the second upside-down

topcombine

#! /usr/bin/env bash
[[ "$#" == 2 ]] || {
	echo Please specify the two input PDF files.
	exit 1
}
PDF1="$1"
PDF2="$2"
PDFALL="all-$(date -I).pdf"
OUTPUTPDF="topcombine-${PDF1%.pdf}-$PDF2"

pdftk A="$PDF1" B="$PDF2" cat A B output "$PDFALL" \
&& pdftops "$PDFALL" \
&& rm "$PDFALL" \
&& pstops "2:0(0,-.5h)+1U(1w,1.5h)" "${PDFALL%.pdf}.ps" "${OUTPDF%.pdf}.ps" \
&& rm "${PDFALL%.pdf}.ps" \
&& ps2pdf "${OUTPDF%.pdf}.ps" \
&& rm "${OUTPUTPDF%.pdf}.ps"

When pdftk isn’t available in more recent ubuntu repositories, you can convert both to ps first and then use psmerge.

Update: Or better (actually simpler than pdftk for this use case), use pdfunite like

pdfunite "$PDF1" "$PDF2" "$PDFALL"