You know what would be REALLY awesome... is if you could have the option to fill out a web form with the interface names for each of the devices you're using, and they will dynamically generate PDFs that match YOUR lab when you download the labs.
For example, if I was using a 3640 for R3 and I had S1/0 and S1/1 rather than the S0/0 and S0/1 that are in the labs, you punch in "R3, S1/0, S1/1" into a form, and bam... the entire lab guide now uses the new interface names.
Lots of work? Yes. Awesome? Yes.