Unless you get the font file itself from whoever created or last worked on the document and used that font (assuming that the font is either an OpenType or a Windows format TrueType font and that you can legally use the font), you may need to separately license Helvetica Neue from any one of the font foundries with a Helvetica Neue family. The name might not match exactly (actually, probably won't match exactly) and you may need to make adjustments in your document to use name of the font that you do license.
FWIW, your experience is not uncommon. There are hundreds of different variants of Helvetica, Times, Arial, etc. that share the same names, but are slightly different. In this particular case, having a slightly different name is probably for the best if you can't get the exact same font, because it will force you to look for any problems that the replacement font may cause (slightly different metrics, styles, etc.).
As far as I know, Apple does not license its version of HelveticaNeue for use on other platforms and even if the font is in OpenType or Windows TrueType format and could be copied to a Windows system, you are probably in violation of the licensing conditions for that font under MacOS X. The closest you may come to the exact HelveticatNeue on the Macintosh may be available from Monotype or Linotype on-line at their web sites.
- Dov
