Preview and iCloud

For a full feature Cloud, I use Dropbox. Here's a file list.

I use Dropbox for:

Images (.jpg, .tiff, .gif)
Music (.mp3, .aiff, .m4a, .wav)
Movies (.mov, .mp4, .m4v)
Microsoft Word documents (.doc, .docx)
Microsoft PowerPoint presentations (.ppt, .pptx)
Microsoft Excel spreadsheets (.xls, .xlsx)
Adobe PDF (.pdf)
Keynote presentations (.key)
Pages documents (.pages)
Numbers spreadsheets (.numbers)
Web pages (.htm, .html)
Text and rich-text files (.txt, .rtf, and many more)

To answer your question, you won't be able to see/use them in iOS. As explained above, DropBox is a much better implementation of a "cloud".

Yeah, iCloud is really more like limbo than heaven. Only certain apps or applications can access it, and even then only their own stuff. It's not like Finder in the cloud. Any of the other cloud services operates more like what you'd expect on a Mac.