How to split a PDF onto multiple pages on command line?

It looks like pdfposter can do this.

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.

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.