File management iPad app
GoodReader may well be just what you are looking for. However it does not unarchive .rars. But it has great File Management, opens most files, and is just amazing. I use it on my iPad for reading journal articles from JSTOR at uni. Great markup tools too.

Also, if you use iCloud Drive and your iPad supports iOS 11, you can upgrade and one of the new features is the built in files app. 
You can look in .zip files on it, but I don’t know if it supports .rar archives