How to print multiple file in Aecosim?

Look into Print Organizer. The Help file has information about how this works.

Basically you create a page definition, select the files to print and assign that definition. Then you can either print it right then, or save off that list as a PSET to use later.

I create page definitions in a DGNLIB file that I can point to with my workspace configuration so that I can use it over and over again. You can make it in the file you are printing from, but then those page definitions are only available while you're in that file.