[NAME] , windows 10 license is injected into the machine BIOS.  Microsoft also has record of your machine hardware ID combined with the license.  If you ever need to reinstall windows 10, it will be reactivated when connecting online.  You won't have to worry about keeping backup of the license. PDF reader is not required anymore.  Web browsers like Chrome, Edge have built-in feature to open PDF files.  Many malware, adware have pop-up when you are online and they have pretext of your computer needed to download or install them.  Do not fall for those scam.  The legitimate software like Microsoft Office, Adobe will provide activation process and you probably have records of purchase transaction.  Those are the records you would want to have backup in case of reactivation. Otherwise, a system backup, a drive image backup, or data backup onto an external drive will be sufficient only if you do it properly and knowing how to restore them when needed. 
Will Dell Back up and Recovery save my Software too, for example my PDF, Word 2021, etc. When or if I have to reinstall Win 10 if I have a problem with PC. Or does a simply creating a Restore Point save my Microsoft authorizing, PDK authorization etc. I have all exterior  1TB Harddrives. thanks 
Dell Back Up and Recovery