Save a edited pdf-File

At first sorry for my english 🙂

Since the last updates of Adobe Acrobat DC, i have a problem with saving documents.

I got the existing document from an other person. When i open it and edit the document and then i press the save button, it

always comes the message:

The document could not be saved. The document is copyright or is in use at an other user. Save the document with a different

name or in an other folder.

Befor the last updates, i had never this problem. Nothing is today different (PC, Apps,...) and there is no other user.

And this is on every pdf-file i get from all persons (different). I know the function to lock the document and others.

But its not locked and 20 different companys that send me pdf-files could not change their behaviour from one day to another.

Its pretty annoying to change always the name and search for the right folder, instead of "save the changes".

It must be a problem with the update, which changed something in the settings?