Questions from iMac to iCloud

I am confused about the workflow when using the iCloud. I have been able to sync my iPad documents to the cloud but am not seeing anything from my iMac there. Also, on my mac I can go to iCloud.com and download a pages document that I created on my iPad to my mac. It opens in pages and I edit it. But how do I get the changes that I made on my mac back to the cloud so I can use it on my iPad?