This can be a little involved if you want to achieve good results. crop marks need to be placed, and a little overlap is typically added in as well.
I’d probably run this through another program entirely. Adobe Illustrator, Photoshop, or Acrobat all have options for Poster Tiling built into their own printer dialog window.
To best take advantage of those you can export from SketchUp to a pdf file. . . or use the OS X ‘save to pdf’ options that are built into the OS’s normal Print Dialog Box. while doing this set your document size to the A1 layout size.
Open the results of this effort in one of the programs I mentioned and send it off to printer again… but this time keep your eye out for Poster Tiling options that are typically found under the Page Handling settings.
If your not interested in going outside of the SkecthUp/Layout workflow, then let me know and I’ll help you out with other options. . . if someone else doesn’t beat me to it.
If we’re to take the SU/LO only approach… then please attach a working file that you’d like to do this on, and we’ll make that happen instead.