Tofutti!
By a series of unlikely links I came across Tofu, a nifty Mac application for reading text horizontally in columns. For some reason I’m not seeing the associated View in Columns service, but I’m not a big user of Services anyway.
Now if only it handled PDFs…
[Update]: I updated to Tofu 2.0 alpha, which does handle simple PDFs, and also noticed this in the Help:
The “View In Columns” service is only available if Tofu is in your Applications folder and you have logged out and back in since installing it. Also, not all applications support Services.