How to combine combine images/pdfs on Ubuntu?

1. Ubuntu 12.04 pdf printer
sudo apt-get install cups-pdf

2. Combine images into a pdf file
imagemagick is a command line toolkit to modify image files
sudo apt-get install imagemagick
convert 1.png 2.jpg output.pdf


3. Combine pdfs into a single pdf file
pdfshuffler is a GUI toolkit for your use
sudo apt-get install pdfshuffler
pdfshuffler