I'm using illustrator, and had many artboards set up. As I was creating more, I noticed that there is a bigger square in which all of the artboards reside. What is it? How do I make it bigger/smaller?
Here is an image to illustrate.
That is the "Canvas" and is limited to about 227.5" x 227.5" or so. The size is a hard limit put in place by Adobe for some reason*. Although some people (like myself and other large format digital printers) hit that limit all the time, I'd imagine only a small fraction of Illustrator user even know it exists.
My suggestion, when projects become larger than the canvas can handle is to work in your own arbitrary scale. It's generally only a few element of the project that have explicit, defined sizes, (for example, a banner width and height) then the rest is all just visually relative.
Illustrator makes working in a scale pretty easy nowadays. Just about every input field accepts basic math, so you can do things like this:
Say you wanted to work at 1:4 (one quarter scale), you could just enter the following:
24/4 (This would give you 24 of your base units, inch, mm, pt, etc, divided by 4 = 6)
Or, you can be specific on the units:
24mm/4 (would end up as 6mm)
Or, you can work in 1:10 (one tenth) scale and just do the math in your head. Move the decimal one place to the left:
24 becomes 2.4, etc.
*I have a theory on the 227.5" limit, but no proof. A signed 16 bit number can store a range of numbers from about -16383 to 16383. If you divide 16383 by 72 (Illustrator's default unit of points) you come up with 227.54166666...
That is the maximum area allotted to each Illustrator file (227" by 227"). You can't make it any larger, but Photoshop or other programs can have larger canvases.
If you need to output your work at a larger scale, you'll need to import it at a higher than needed resolution into Photoshop (for example). Then change the resolution without resampling.