Tabula is an amazing piece of software, especially when it Just Works. But, if you use it enough, eventually you have to hold its hand and tell it where all the columns are on a page in pixels or percent of the page. This simple script lets you produce that configuration string by placing lines on an image of your PDF from your browser.
Run the command:
make start PDF=./path/to/PDF.pdf
Then go to http://localhost:8080 in your browser.
To use it, click between each column, placing a line in its place. The configuration will be generated beneath the PDF image. Copy it and provide the string as the argument to tabula's -c option. You can move between the pages of your PDF by clicking the Next button. The clipboard button will copy the string to your clipboard.
You just need the convert command, gs command, Python 3 and optionally make.
Ubuntu dependencies:
sudo apt install imagemagick make ghostscript
If you don't have make, but you do have convert and gs you can still run everything by running all the commands inside the Makefile individually.