What does this error mean? "ERROR: Document is malformed or contains code which may cause an external action (such as launching an application). This PDF document cannot be accepted."

The PDF file needs to be flattened prior to uploading it to CM/ECF. Follow the steps below to correct the issue.
Print to PDF (Windows)
•   Open a file in a Windows application.
•   Choose File > Print.
•   Choose Adobe PDF as the printer in the Print dialog box.
•   Click Print. Type a name for your file, and click Save.

Print to PDF (Mac OS)
The Adobe PDF printer is not available on Mac. However, you can use the Save As Adobe PDF option to print a file to PDF on Mac.
•   Open a file in a Mac OS application.
•   Click the PDF button and choose Save As Adobe PDF.
•   Choose the Adobe PDF Settings and click Continue.
•   Type a name for your file, and click Save.

NOTE:
PDFs with the following content will be rejected after the upgrade to CM/ECF NextGen v1.6 :
•   Does not comply with PDF format standards
•   Contains JavaScript
•   Encrypted or password-protected
•   Contains scripts which can launch an external application
•   Contains internal attachments
•   Contains audio and video content
•   Created with Mac OS X using a fillable form in the Safari browser
•   Created with Mac OS X using MS Word and selecting the option, “Best for printing”