I'm sending a Barcode image to a PDF. On some printers if prints fine, on
others its all speccy and mushy looking. Now the Image format I'm using
Jpeg, can a Jpeg be reduced to 2 colors and no antialiasing?

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JPEG is a lossy compression system which encodes the image in a
frequency-space representation. If you encode a black & white image,
you get very high frequencies in the image, which tend to get filtered
out by the compression system. When JPEG is rendered (decompressed),
the reconstructed image will only have lower frequencies, which means
that in effect, you'll get a blurred image (this is an approximation
of what really happens, but it gives you a rough idea).

So the answer is : don't use JPEG for black & white images. Prefer
GIF, PNG, TIFF, BMP or whatever.

Pierre