I've found the following iPad tools invaluable for handling text files, zip files, uploading and downloading arbitrary files:
1. Textastic - programmer's plain text editor, line-oriented, can handle a choice of newline endings, handles UTF-8 iirc saves to local file system or to the icloud.
2. Documents by Readdle, acts like a mini file system, and a file manager, is a file viewer, and opens zip files. Displays plain text and PDFs and acts as a save-target so you can save-as to Documents from within another app. So just investing in this one app extends every other app you've got. Facilitates exchanging files between apps.
3. iCab web browser. This full-featured web browser is what you need for uploading files, arbitrary files, binary files, files taken from the Documents file system. Need to reflash a device or program a device by uploading some config file in some don't know, don't care content type. Then iCab will do it. iCab will also do the job when Safari seems to refuse to download or upload something. In any case, you probably don't want to download using Safari anyway as you file will be buried in limbo in some isolated store of its own, better to download and saveas into the Documents store.
4. The iDiff tool. Just differences a pair of text files. That's it. Just works. £1.49! You need this.