combining files and saving

I'm using Abode Acrobat Premium on my iPad and I want to be able to take two or more files from Dropbox and combine them and then save them back to Dropbox. I can open the files in Acrobat and combine them but I can't figure out how to save them back to Dropbox. The combined file is in the Adobe Cloud but I try to find it in the 'Files' app on the iPad and I don't see an option for Adobe Cloud (or something like that). I the rare occasion I do get something to work, I don't write down what I did and the whole process seems very cumbersome. Can someone help?