If the contents of a page that save_pdf is rendering is exactly the size of that page -- for example, left page margin + three cards + right page margin is exactly the same width as the page -- then save_pdf thinks it doesn't fit and will render one fewer column than would actually fit.
(This is of course easy to work around by simply subtracting a pixel from the page margins, but still annoying.)
If the contents of a page that save_pdf is rendering is exactly the size of that page -- for example, left page margin + three cards + right page margin is exactly the same width as the page -- then save_pdf thinks it doesn't fit and will render one fewer column than would actually fit.
(This is of course easy to work around by simply subtracting a pixel from the page margins, but still annoying.)