I'm not sure this is an answer, but IMO the simple solution would be to take the "big binder" and scan or convert the native files to .PDF format, and store it where you want.

A couple of advantages that I see:

1. At least in the U.S., .PDF is nearly universal, as .PDF readers are widely available (for free) for computers and most, if not all, smartphones.

2. Converters to produce .PDF files from scans or native file formats (e.g. MS Word) are also widely available, (some versions of MS Word will do this for you).

So, no special "app" is needed to produce or read the file.