CloudDocs > session folder filled with version of a Pages file I'm on a 2016 MacBook Pro with macOS 10.13.5

In (User)Library/Application Support/CloudDocs there is a folder called session weighing approx. 35GB.
Inside there is another folder called r(why r?) which contains a few thousand files, 99% of which are what seem to be incremental versions of the same Pages document. 

Why are those files there? 
Can I safely delete them? (for your knowledge, I have already copied the original final version of the file elsewhere for backup, just in case).

What is the use of this folder (apart from being the iCloud Drive mirror on the computer's drive)?
I don't know the answer to your question, but I have the same folder which is also huge. I'm pretty sure they are indeed incremental files.
I have a few different ones, but there's not one for every Pages file I own, which makes me believe they are the files I wanted to "revert". There's an option in Pages, Preview, Keynote, Numbers and more Apple applications that lets you revert to a previous version. I think what happened is that it saved all previous versions.

I just opened some of those files and tried to revert them, but they don't even revert back to all of those saves! Those gigabytes of files are there but I can't open them and I can't revert to them.
I deleted all of the versions of one document and opened the actual one, the document was still complete.
I did the same with another and the actual document is fine. I think you might be able to delete all of it. Maybe make a backup before you do so if it's an important file.