Create a pdf file (chop, rotate and convert png to pdf)

gistfile1.txt

# Chop the figures (in my case, figures were in landscape mode)
for i in $(ls *.png); do j=$(echo $i | sed "s,.png,-chop.png,g"); convert $i -gravity South -chop 0x10 -gravity North -chop 0x50 -gravity East -chop 296x0 -gravity West -chop 296x0 $j; done

# Rotate the figures 90 degrees (clockwise)
for i in $(ls *-chop.png); do j=$(echo $i | sed "s,-chop.png,-chop-rot90.png,g"); convert $i -rotate 90 $j; done

# Convert all figures to PDF
for i in $(ls *-chop-rot90.png); do j=$(echo $i | sed "s,-chop-rot90.png,.pdf,g"); convert $i $j; done

# Unite all PDF (21) files into one
pdfunite $(echo {1..21}.pdf) artigo.pdf