Helvetica font changes to Arial when the document is printed to a PDF
There are five (5) standard fonts in PDF that are not embedded by PDF applications by default. The assumption was that these are standard fonts and everyone already has them on their computer.
These are the fonts that are not embedded by default:
Times (regular, italic, bold, and bold italic)
Courier (regular, oblique, bold and bold oblique)
Helvetica (regular, oblique, bold and bold oblique)
This is a MAC vs Windows difference. Helvetica is a standard font on the Mac, equivalent of Arial. Helvetica does not exist on Windows by default, so when a Mac generated PDF is opened on a Windows machine and conversion is done, it will replace Helvetica with something else. The closest font to that on a Windows system will be Arial so that is what will be used.
Most PDF applications have an override like Power PDF on Windows to allow a create of a PDF to override the default Embed Non-Standard Fonts and Embed all Fonts when a PDF is saved. This setting is called Font Embed in the Power PDF Create Assistant settings under profiles.