Programatically set version

Currently I use this to build a new exe:

“C:\Program Files (x86)\Paquet Builder 3\pbuilder.exe” myProjectFile.pbpx /c /s

How can I set the version info on the output exe file?

The sole way to modify a project (without hacking the PBPX file with 7-Zip for instance because it’s just a Zip) externally is through directives. See About Directive Files - Paquet Builder Documentation
Example:

ProdVerNum: sets the package’s file product number in the Version Information resource.
FileDesc: sets the package’s file description in the Version Information resource.

And so on.