While trying to export an InDesign file in to PDF getting " Background Task alert"

I have had this problem a couple of times and it can be two reasons:

1. you are trying to export it to a folder that has permissions on.

2. you have a bad image in there.

if it's the later, you'll have to trial and error each image by removing it and re-exporting until you find the image that the problem lies with

Being in your shoes I would try to abandon PDF export as a background task, and go back to 'old school' routine.

Try Solution 4 from here:

https://helpx.adobe.com/indesign/kb/pdf-export-background-task-hangs.html

Hi,

There are multiple factors both internal and external to InDesign application that can lead to document corruption. However, we can take a look and see if the file can be repaired. Please email your InDesign file to corrupt_indesign_docs@adobe.com and we will take a look at the document.

If the file is larger than 10 Mb, you can zip (and password protect) the file and upload to Creative Cloud account (or Dropbox) and send us the document link.

Regards,

Himanshu Kapoor

A method that has been sometimes successful for me in removing background corruption in a file is by moving all of the pages of the infected document to a brand new one of the same size using the Pages Panel. To do this place the old document over the new one with the pasteboard of the new one showing. Make sure that all Master Page items for all of the pages are unlocked and select all of the pages in the Pages Panel. Drag all of these pages directly from the panel onto the pasteboard of the new document. You'll get a prompt as to where you want the new pages placed. Click OK and the pages from the old document will now be a part of the new one.

I've seen this method clean up some really strange stuff in my ID files.

I wrote an FAQ for this type of dilemma

Re: File Crashing on Output - printing/PDF/other

Here are some things to try:

• Export the file as IDML and reopen it in InDesign. Try to make the PDF again.
• It's possible there's something bad in your InDesign file. To figure out where it is, delete the second half of the file and see if the PDF export works. If not, undo that and delete the first half. Export the PDF again. Whichever part doesn't work contains something bad. Repeat this process to narrow it down to the page and see what might be causing the problem.

Good luck!