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I'm not sure if this is the easiest way, but I download the document to be edited, make the changes in Word or Excel, and then save as. I modify the name of the document, and upload it back to my iCloud account. I dislike having different variations of the same document, so I usually delete the previous editions. This is not idea, I know, but it works for me! I'll be interested to see if anyone else posts a better solution!
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