It's going to depend on the printer driver you are using. Since you are going to file you can probably pick pretty much any printer driver you want.
I did some testing and the HP Universal Printer Drivers (as an example) will go up to 600DPI when used with a file (they claim 1200DPI, but it's not actually available).
You can get the 32-bit version of the HP UPD here.
One of our B&W laser here is a Brother 1650DN, and it supports up to 1200 DPI. If I use its driver for a new printer that prints to FILE: I can pick 1200 DPI -- so there are drivers out there that'll do >300DPI, you just have to find one that works. :)
Also, ensure that whatever you're printing is in a resolution that high, or you're just printing a 300 DPI (or worse, screen DPI of like 72) at 1200DPI, so it'll look the same even with the higher output DPI.
Thanks. I'll see if I can't grab the Brother driver, that sounds promising. And, FWIW, it's a Word Doc, so it should be printing the TTF of the document, which is a vector? – Eric Martindale – 2010-06-23T03:37:17.427
Yeah, you should be fine with the fonts. Any pasted images will have to be of print resolution before paste, and then scaled to the preferred size inside Word. This keeps the res. up during printing for the images; makes the Word file huge though. ;) – Ƭᴇcʜιᴇ007 – 2010-06-23T17:29:37.670