For those following along I've done some testing with this action.

For each converted document, docx to pdf in my case, it will use 2 api calls against your cloudmersive license. I'm testing with the free edition at the moment.

Based on that the cost of the api plans are not too bad from cloudmersive.

Every converted file will output to a file variable with the file name 'output.pdf'

So if uploading to sharepoint or other file store you will need to store then rename / update.

@rickdemarco  posted a replay to this post a short while ago on an upcoming feature to be able to rename files. I think that would be very handy with the output of this action.

How to rename the file name? - Nintex Community