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Okay, I snipped everything, because my answer is way shorter than the
quoted material would have been...
Helvetica is resident on PostScript printers. It has the same metrics as
Arial. If you lack Helvetica on your computer, because the various
software versions you have installed didn't come with it, go ahead and
use Arial. In your printer properties, specify substituting printer
fonts for TrueType rather than downloading outlines, and the printed
output will use Helvetica.
As to why you don't have Helvetica on your system, it's either because
you really do have it but just haven't found it yet (sometimes fonts get
installed in odd directories) or it's because Adobe decided to change
the package they include in ATM.