source of downloaded files "Where From"are not showing anymore

Hello there

I download a lot of PDF files from the internet to use in my business researches, many times when I want to get more details about a topic I go to "get info" and then "where from" in order to refer back to the website or source of file (which is very useful for me).

Recently, I am checking my files and all of them are not showing the source/where from downloaded.

I think the reason is because I used a 3rd party application "cleanmymac 2" to delete old and unused files in order to enhance the performance of my Mac.

Please, can anyone tell me how to remove old files to save space and performance but without losing the "where from"/source of downloaded files?

Many thanks