overlay one pdf with another from the command line: pdftk alternative?

Question

I use a bash script to auto-generate a pdf calendar each month.I use the wonderful remind program as the basis for this routine. Great as are the calendars I get using that program, I need a more detailed header for the calendar (than just the name of the month and the year). I couldn't puzzle out a way to get the remind program to enhance the header, but I was able to get the enhanced results I wanted by creating a second pdf containing the header enhancements I need, then overlaying that pdf onto the calendar I produce with remind, via the pdftk utility (pdftk calendar.pdf stamp calendar_overlay.pdf output MONTH-YEAR-cal.pdf). Unfortunately, I recently lost the ability to use pdftk since keeping it on my system would necessitate me ceasing to do other system updates. In short, I had to remove it in order to continue updating my system.

So now I'm looking for some alternative that I can incorporate into my bash script. I am not finding any utility that will allow me to overlay one pdf with another, like pdftk allows. It seems I may be able to do something like what I'm after using imagemagick (-convert), though I would likely need to overlay the pdf with an image file like a .jpg rather than with a pdf. Another possible solution may be to use TeX/LaTeX to insert text into the pdf as described at https://rsmith.home.xs4all.nl/howto/adding-text-or-graphics-to-a-pdf-file.html.

I wanted to ask here, before investing a lot of time and effort into pursuing one or other of the two potential options I've identified, whether there is some other way, using command line options that can be incorporated into a bash script, of overlaying one pdf with another in the manner described? Input will be appreciated.

LATER EDIT: another link with indications how to do such things using LaTeX https://askubuntu.com/questions/712691/batch-add-header-footer-to-pdf-files

Answer 1

Assuming for simplicity that both of your files are of size 500pt x 200pt, you can use pdfjam with nup and delta options to trick it into overlaying your source pdf files.

pdfjam bottom.pdf top.pdf --outfile merged.pdf \
    --nup "1x2" \
    --noautoscale true \
    --delta "0 -200pt" \
    --papersize "{500pt, 200pt}"

Unfortunately, I've found in my tests that I needed to increase the y delta by one point to get perfect alignment.