set password for a pdf-file

To add a password to a pdf you can simply use pdftk and have it add a password as follows:

pdftk original.pdf output new.pdf user_pw PROMPT

You will get a prompt asking for the password, which in turns will be added to your pdf-file.

imagemagick convert pdf to jpg

To convert a pdf file in a image file, the best option is to use imagemagick, which means convert. The only option you have to define is the density, which can be defined as follows:

convert -density 300 test.pdf test.jpg

pdftk extract pages of pdf-file

Extract PAGES from input.pdf into output.pdf via:

pdftk A=input.pdf cat A${PAGES} output output.pdf

for more information use:

man pdftk

Imagemagick compose two images

convert pdf into png

convert -density 300 -depth 8 -rotate -90 -quality 85 test.pdf test.png  

compose an inlet into an background:
while resizing the inlet by 15% in both directions
and shifting the inlet by +700 +0

composite -verbose -geometry 15%x15%+700+00 inset.png background.png test.png