How do I join multiple pdf files of different dimensions?

Question

I need to join multiple pdf files into a single page pdf. I need to stitch together some PDFs that I generate. If I am stitching horizontally, all of the PDFs are the same height but not the same width. When I am stitching vertically, all of the PDFs are the same width but not the same height.

I found lots of answers saying to do this with pdfjam/pdfnup. I tried that, but it seems that is only for when each item to be joined is the same dimension, or else I just can't get it to work right.

I would really prefer to do this in ghostscript, since the rest of my PDF manipulation is already done in ghostscript. I haven't found a solution for that though.

As an example, the items I am stitching together look pretty much like this:

┌---------------------------------------┐
┬-┬----------------┬-┬----------------┬-┬
| |                | |                | |
| |                | |                | |
| |                | |                | |
| |                | |                | |
| |                | |                | |
| |                | |                | |
| |                | |                | |
┴-┴----------------┴-┴----------------┴-┴
└---------------------------------------┘

I am first trying to join the 5 boxes that form the center section horizontally. Then I need to join that with the boxes above and below it.

Answer 1

My answer here contains a PostScript program which will work only with Ghostscript and only with versions up to 9.26 but does imposition.

That program does a load of stuff you won't want, it assumes you are trying to fit the 2 input pages onto a specific size of media, and scales and rotates the pages to make the best fit. You won't want to do any of that.

Essentially you want to move the current point to the start of each page, draw the page content, then move the current point to the start of the next page, draw the content of that page, and so on.

In broad terms, this:

%%
%% First we open the PDF file
%%
File dup (r) file runpdfbegin pop
process_trailer_attrs

opens the PDF file then this:

  pdfgetpage                                             %% get the page from the PDF file, stack: -save- -save- loop -dict-
  dup /Page exch store                                   %% save a copy of the page dict inside itself
  pdfshowpage_init                                       %% initialise the page
  draw_page_content                                      %% se above, draws the graphical objects, stack -save- -save- loop

draws a page (pdfgetpage takes a number, starting from 0, for the page to draw from the PDF file).

This:

PageXTx PageYTx translate                                %% Move to draw page 2

Moves the current point.

So that's all the operations you need, putting them together is up to you. You will need to work out the size of the total final 'page', and start Ghostscript with that set as the media size (use -dDEVICEWIDTHPOINTS and -dDEVICEHEIGHTPOINTS) then you'll need to work out the position on that page of each of the 'sub pages' (bear in mind that the origin is at bottom left for PDF) move to that location, draw the page, repeat for each page.

Finally you will need to execute:

showpage

so that the final drawn page is flushed, and then ideally:

//runpdfend exec                                             %% End the PDF file

So its possible, but as you can see, non-trivial in the current implementation. Again let me point out that this will NOT work with versions of Ghostscript greater than 9.26.