Yes I can flatten other PDF files with the exact same DDX without any problems. Only with some PDF files it generates this exception.

<?xml version="1.0" encoding="UTF-8"?> <DDX xmlns="http://ns.adobe.com/DDX/1.0/"><PDF result="out.pdf"><NoXFA flatten="true"/><NoForms/><PDF source="0.pdf"/></PDF></DDX>

I use SOAP to call the AssemblerService.invoke method and pass the DDX and the input PDF documents as parameters.

But I can open the PDF file that causes this issue with the AssemblerService of AEM Forms in the Adobe Acrobat Reader 2017 without any problems. So the PDF file seems to be not invalid or corrupted.

We have the same problem with some PDF files: [3/15/21 15:20:14:433 CET] 00003ca9 AssemblerServ E TRAS0014I: The following exception was logged com.adobe.livecycle.assembler.client.ProcessingException: ALC-ASM-S00-002: Failed to execute the DDX - error messages provided.at com.adobe.livecycle.assemb...