Can't save: "The file may be read-only, or another user may have it open. Please save the document with a different name or in a different folder."

Another Solution is to open your Antivirus program and check the allowed and blocked apps and make sure to place the illustrator.exe file in the allowed apps so that the Antivirus program doesn't automatically stop it from making changes to your files

Disable the preview pane in file explorer and it worked for me.

Adobe seem to register the file as being open when you click on it without opening it and it shows the preview.

Just disable preview pane or select a different file and that should help.

I wasn't using any cloud-based file shares or network shares, so I kept looking in this thread for something close to my problem. I got a clue from the entry by cheyennew74060576 and based on that message, I figured out that the cause of my issue was Windows (SHOCKER!). Their ransomeware protection is a bit overzealous...

Here are the steps that worked for me...I'm running Windows 10, version 21H1 (Build 19043.1202):

• First, open Acrobat and attempt to save. It is critical to actually try to save a file and see that it fail - the failure needs to be recent so it shows up later in these steps.
• Click the Windows button
• In the "type here to search" box, enter "controlled folder access"
• Click on "Allow an app through Controlled folder access"
• If prompted to allow changes to your computer, click [Yes]
• Click the [ + Add an allowed app ] button
• Click "Recently blocked apps"
  In the "Recently blocked apps" pop-up window, you should see an entry for Acrobat.exe near the top of the list. To allow Acrobat to save, click the big "+" to the left of the Acrobat.exe entry.
  • If you do not see Acrobat.exe, you may need to click the link to "Browse all apps". This will open a standard Windows "Open" dialog. Navigate to where Acrobat.exe is located (the default for Acrobat DC is C:\Program Files (x86)\Adobe\Acrobat DC\Acrobat\Acrobat.exe"). Select it and click [Open].
• Close out of any open dialogs, making sure that Acrobat.exe is now listed in the "Allow an app through Controlled folder access" dialog.

I hope this helps others!

After I received this message while trying to save the file in Windows, I switched the save location to Desktop, saved it there, and then moved it from the Desktop to the location where I wanted to save it.

This wont help everyone, but if you have Adobe Illustrator, open the PDF using that application, then simply 'save as' and choose PDF format.

Error : 

Fix to save the file on cloud. 

Step -1 Pause the sync 

Step -2 Go to any file > Click Save as >  Rename the file  for example : Parris.com rename it to Parris.comm > then you would be able to save the document. Once the documents is saved then rename back to Parris.com. Then start the sync. That's it. Now you can see all the files synced successfully to OneDrive , Google drive. 

Thanks, 

Ravi Kumar 

that worked!  Gracias, I have spent hours trying to resolve this issue.  it just started happening, not sure how it got changed to begin with.  thanks!  Don

Suspending cloud storage sync helped me

Just wanted to add this as an alternative.  

- Open your File Explorer

- Click on View

- Click on Preview Pane to turn if off. 

This helped me when my users were experiencing this issue. 

I had this problem, and it was because I had moved the file to a different folder while it was open on my Mac. Adobe Acrobat appears to have issues with that.