I'm trying to send a file for a label as a PDF and the text is white. Is there a way that I can make the art board transparent so that she can see it without me saving it for web?
The proper way to send a single color file for reproduction is to send black artwork. Then the printer will put white ink on the press. You don't need to send white artwork. For commercial printing white equals not there or invisible.
If you really, really, really want to send white artwork, then send a negative of the artwork. That is, add a black background. That will allow the print provider to merely create a reverse and use that for production.
Talk to the print provider. Chances are very high you don't need white artwork.
In either case, for commercial printing, PDFs never need to have a transparent background.
If your client is using Acrobat Reader to preview the image, she can click Edit > Preferences > Page Display, and select the option to show the transparency grid.
As far as printing in white is concerned, are you absolutely sure about that? Have you discussed this with your printer? Most printing processes do not involve printing in white ink.
Since version 1.4, PDFs support transparency. The white background is usually added automatically by the application that you use to view the document, not by the one that was used to create it.
For example, in Acrobat settings do Cmd+K > Page display > Transparency grid to see a transparency grid similar to Photoshop's.
You can open the documentin Photoshop to confirm that the background should really be transparent.