Quit Acrobat.
Last updated on
Sep. 28, 2022
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Also applies to Adobe Acrobat 2017, Adobe Acrobat 2020
A running instance of Acrobat has caused an error
In Acrobat, trying to use a tool or feature results in the following error:
"A running instance of Acrobat has caused an error."
Reason: The error occurs when an already launched instance of Acrobat is busy or in a hang state and you try to perform some operation from outside Acrobat, for example, opening a PDF file by double-clicking.
Solution
To resolve the problem, try the following solutions in the order they appear below.
Solution 1: Quit Acrobat and kill all the previously running Acrobat processes
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Do one of the following to open the Task Manager:
- Right-click Windows Taskbar and then click Task Manager.
- Press Ctrl+Alt+Delete keys together and then click Task Manager.
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Right-click Adobe Acrobat and then click End task. If you see more Acrobat processes in the Background processes list, right-click on each process one by one, and then click End task.
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Close Task Manager.
Relaunch Acrobat and see whether the problem is resolved. If not, try the next solution.
Solution 2: Registry fix
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Quit Acrobat.
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Open the Windows Registry Editor:
- Click Start > Run.
- Type Regedit in the Open field and then click OK.
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Navigate to the following registry key:
HKEY_CLASSES_ROOT\acrobat\shell\open\ddeexec\application
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Take a backup: Right-click the Application key and then click Export. In the Export Registry File dialog box, enter a file name and click Save.
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Change the value of the key from AcroViewA20 to AcroViewR20 (where the last two digits or numbers depend on the Acrobat version installed on your computer; For example, for Acrobat 2020, it will be 20):
- Double-click the Default under Name. The Edit String dialog box is displayed.
- In the Value data field, change the value to AcroViewR20 and then click OK.
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Close the Registry Editor by clicking the Close icon (X) at the upper-right corner of the dialog box.
Relaunch Acrobat and see whether the problem is resolved. If not, try the next solution.
Solution 3: Update Acrobat to the latest version
- To automatically update from Acrobat, choose Help > Check for updates. Follow the steps in the Updater window to download and install the latest updates.
Relaunch Acrobat and see whether the problem is resolved. If not, try the next solution.
Solution 4: Repair Acrobat
Acrobat or the resources it depends upon could be damaged. Try repairing Acrobat as follows:
- Run repair from within Acrobat: Choose Help > Repair Installation.
Solution 5: Disable the anti-virus program
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Check whether an Anti-virus program is installed on the machine.
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If yes, disable the program. Check whether the problem is resolved.
If the problem is resolved, report the problem to the corresponding vendor.
