Go to System Preferences > Security & Privacy, and then choose Automation on the Privacy tab
When Acrobat tries to access other apps on macOS Mojave 10.14, an authorization dialog box appears asking users to allow access or control to the app.
Similarly, when an app tries to use Acrobat, an authorization dialog box appears asking users to allow control over Acrobat.
Features or workflows related to the conversion of Microsoft Office files (Word, Excel, PowerPoint) to PDF from Acrobat display the authorization dialog at the first instance:
*The thumbnails of files don’t get generated in the Combine dialog box.
In the authorization dialog box, select OK to allow control or access. The dialog box doesn’t appear for the same app the next time.
If you select Don’t Allow or Not Now, the feature or the workflow fails, and all future conversions will also fail unless the corresponding security setting is changed.
To change the security setting, do the following:
Go to System Preferences > Security & Privacy, and then choose Automation on the Privacy tab
In the right panel, under Adobe Acrobat, select the check boxes for the applications to which you want to allow access or control.
If you use Firefox to convert web pages to PDFs, select the Adobe Acrobat check box under Firefox.
Restart Acrobat, and then use the Create PDF workflow.
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