The document could not be saved. The file may be read-only or opened by another user.

When try to save a pdf file, you may get this error as the below screenshot.

Currently we can reproduce the issue when Adobe is the default previewer in Preview Panel.

Solution

Please set Foxit preview handler as default again by doing the followings：

1. Firstly close all folders (windows explorer windows).

2. Press "Window + r", input "regedit" press Enter to open your Registry Editor.

3. Go to HKEY_CLASSES_ROOT\.pdf\shellex\{8895b1c6-b41f-4c1c-a562-0d564250836f}, 
check the value for items under {8895b1c6-b41f-4c1c-a562-0d564250836f}, change them to 

{1B96FAD8-1C10-416E-8027-6EFF94045F6F}.

4.Go to HKEY_CLASSES_ROOT\WOW6432Node\CLSID\{FFBD7029-84D7-4E1E-BE44-B6619BC545ED} ,change the value for the AppID string into

{534A1E02-D58F-44f0-B58B-36CBED287C7C}

5.Go to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\CLSID{DC6EFB56-9CFA-464D-8880-44885D7DC193},change he value for the AppID string into
{534A1E02-D58F-44f0-B58B-36CBED287C7C}

6.Go to HKEY_CLASSES_ROOT\WOW6432Node\CLSID\{1B96FAD8-1C10-416E-8027-6EFF94045F6F}\LocalServer32, check the value for item under LocalServer32, change it to "path\FoxitPreviewhost.exe"

For example: I have Foxit PhantomPDF installed under C:\Program Files (x86)\Foxit Software\Foxit PhantomPDF\,

so I have to change the value for the item under LocalServer32 to

C:\Program Files (x86)\Foxit Software\Foxit PhantomPDF\Shell Extensions\FoxitPreviewhost.exe

5. Then try to open your file, change and save.

If Adobe still keep on setting itself as system default previewer on your computer somehow,please choose to disable Adobe PDF file preview in File Explorer preview pane, use these steps:

1. Launch Regedit.exe and navigate to the following branch:

   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers

2. From the File menu, choose Export… and backup the branch to a REG file.
3. Right-click the GUID for Adobe PDF Preview Handler which is usually                   {DC6EFB56-9CFA-464D-8880-44885D7DC193} and choose Delete.
4. Click Yes when prompted for confirmation.
5. Exit the Registry Editor.
6. Logoff and login back for the change to take effect.

When you need to enable Adobe PDF Preview handler again, please add the value

{DC6EFB56-9CFA-464D-8880-44885D7DC193} back for the Adobe PDF Preview Handler GUID.