Is there a command-line method to split a gigantic single-page PDF file into one file with multiple pages?

Actually mutool has almost the same syntax as the one you're suggesting (are you its author ??) :

mutool -x 2 -y 3 sample.pdf sample-2x3.pdf

To install mutool, just install mupdf, which is probably packaged with most GNU/Linux distributions.

It looks like pdfposter can do this.

Take a look on http://www.graphviz.org/doc/FAQ.html: Q14. How can I print a big graph on multiple pages?

The page attribute, if set, tells Graphviz to print the graph as an array of pages of the given size. Thus, the graph

digraph G { page="8.5,11"; ... }

will be emitted as 8.5 by 11 inch pages. When printed, the pages can be tiled to make a drawing of the entire graph. At present, the feature only works with PostScript output. Alternatively, there are various tools and viewers which will take a large picture and allow you to extract page-size pieces, which can then be printed.

ONLY Postscript! But for automation no showstopper :-). Just let ps2pdf run over it. It worked for me.

Several linux utilities come to mind:

(from their man pages)

pdfseperate [options] INPUT.PDF OUTPUT%d.PDF

reads INPUT.PDF, extracts one or more pages, and writes one PDF file for each page to OUTPUT%d.PDF (%d is placeholder for page number) (from 'poppler-utils' package)

pdftk INPUT.PDF burst

reads INPUT.PDF, producing one or more PDF files containing individual pages, named 'pg-XXXX.pdf' (unless output filename specified) (from 'pdftk' package)