PDF export background task hangs | InDesign CS5, CS5.5
Exporting to PDF (Print) results in a hung background task that cannot be cancelled. If you attempt to quit InDesign, you get the message, "InDesign cannot quit because one or more tasks are running in the background."
Solution 1: Install the latest InDesign updates.
Install the Iatest InDesign updates by choosing Help > Updates, or by visiting the Adobe product updates page: http://www.adobe.com/downloads/updates
Solution 2: Disable preflight and restart InDesign.
Choose Window > Output > Preflight.
Deselect the On checkbox.
Quit InDesign and restart it.
Export your document to PDF.
Solution 3: Add the document to a new book and export from the book panel
Choose File > New > Book.
From the Book panel, click Add Documents.
Select the INDD document that is affected and click Open.
From the Book Panel pop-up menu, choose Export Book to PDF.
Solution 4: Disable background exporting
Create an empty text file and save it as "DisableAsyncExports.txt".
Navigate to the location of the InDesign executable, for example:
Win: C:\Program Files\Adobe\Adobe InDesign CS5\
Mac: /Applications/Adobe InDesign CS5.5/Adobe InDesign CS5.5.app/Contents/MacOS/
Move the text file from step 1 into this location.
Note: For a startup script that provides a menu choice to control background export, see this link.
InDesign CS5 introduced PDF export as a background task via multi-threading capabilities. Some third-party and InDesign native operations become confused by this new method and result in a hang.