I didn't think that generic "sans serif" had any real meaning. I thought it was....I want to say "family" but I don't think that's the word I'm looking for. But I didn't think it was actually a font. However, it seems that I can indeed type with it....
If I type with it (on Windows 7), and compare to the same size (and line spacing) as Verdana, they are very close, but not identical.
Placing one on top of the other, it appears perhaps the only difference is kerning. However, notice the capital Q, J, and I are quite different.
The red is "sans serif", the black is Verdana.
Edit
I'm not sure about that technique of using Adobe Reader to determine what type of font is being used. Maybe Adobe Reader has just chosen Verdana because it's the closest? Which option did the user choose when they saved as PDF?