Can anyone tell me if the vba compiler compiles all the code in every module
at once for a workbook, or does it compile the code in the modules as they
are called?

Can I place code that will not work on all computers in a module by itself,
and have Excel still operate without compiler errors if the module containing
the offending code is not called?

I have code for creating pdf files that works on computers with PDF
Distiller. I want to have the code available to those computers, but still
run without compiler errors on computers without PDF Distiller.