Helvetica is a rather popular font, but due to its license, it’s not available on all platforms, e.g. Debian/Linux. There are a few alternatives, though.

As we can see, both `Free Helvetian` and `Nimbus Sans L` are pretty close. `Nimbus Sans` is slightly thiner, but works perfectly as a substitute. (Actually, `Nimbus Sans` is the substitute for `Helvetica` on my Debian/Linux.) Even though the first two share the largest resemblance with `Helvetica`, they are only available in PostScript (`pfb`) format, which has been mostly rendered obsolete by OpenType. Therefore, I suggest using `Nimbus Sans` as the alternative to `Helvetica`.

The source of the pdf is shown below. One should compile it using `xelatex main.tex`. If you system doesn’t have `Helvetica` yet, you can download it from https://www.fontmirror.com/helvetica for testing purpose. (Don’t forget to update the path to it in the tex file.)