There is another way you can upload to iCloud without using the web interface. This will only work when you want to upload to iCloud, once the document has been uploaded via this method you have to download it via the iCloud website.
The location you need to look at is :
For this you will need to get access to your Library folder, if you are unsure on how to make it visible then I recommend you read this post which details the steps.
In here you may have more directories for applications that can use iCloud, but you should see :
All you need to do is drop/copy & paste your document into the documents sub-directory in the relevant application directory. It will be converted into the format iCloud uses and within a very short time you will be able to see the document on your iOS device.
It converts it into a directory, and inside there is a plist file, and index.db file and a preview directory. As I mentioned once you have copied them into here you won't be able to download from this directory.
This could save you a lot of time if you have multiple documents that you want to upload to iCloud, or after you have made some changes you could just drag the document back into here.
I am always interested in feedback so please feel free to add any comments, or you can mail me here. If you would like to submit a quick tip with full credit and links back to your site then also feel free to contact me.