What is the format?
It would be guessing if we told you what format is the one they give.
This strongly depends on the conference or fair; some may give zip files, some may give paper, and some may give both (I doubt they give none). If you want to know if a specific conference offers their resumes on zip files I suggest you contact them to ask for this detail to get a better answer.
We can't afford an ATS just yet so I wanted to know because I dont want to scan resumes one by one so I can have lots of people view them.
As I see this you have two scenarios:
They don't give zip files. For which you will have to prepare yourself to be able to scan any resume you get on paper (hopefully other conferences do give zips).
They give zip files. In which case no problem, as you can easily share them with others for consideration.
I suggest you give both of them a thought so you can better prepare yourself for this task in case you do have a lot of papers to scan. Be sure to inform about this to whomever you consider necessary so they are aware of this.