Combine Multiple Files won't allow .ai files

[TJL429]

I am currently running Acrobat Pro DC Version 2020.006.20042 on Mac Catalina. Combine Multiple Files will no longer allow .ai files to be used for creating a .pdf file.

[ls_rbls]

I assume this happened after a recent update was applied through the Creative Cloud Desktop app?

[ls_rbls]

++ To JR's valuable guidance also see if any of this dicussions can help:

•  https://community.adobe.com/t5/acrobat/can-t-combine-files-into-one-pdf/td-p/10112049?page=1

• https://community.adobe.com/t5/illustrator/merge-artboards-from-several-ai-files-into-one-ai-file/td...

Also check here for known issues:

• https://helpx.adobe.com/acrobat/kb/known-issues-acrobat-dc-reader.html

As far as I can remember this issue happened to another user last year. 

In the  case of macOS it seems that some of the tips that may work on a MS Windows environment may not necessarily work with mac.

TIP: 

A possible work around (long method),  rename the ai. files with a .pdf extension and see what you can achieve.  Test with otwo or three copies of .ai files, of course, not all of them. And see what results you get.

[TJL429]

Correct. 

[JR Boulay]

I guess this is because these Ai files are not saved with the "PDF compatibily" option ticked.

See this article about Ai/PDF files (Google translate is your friend): https://www.abracadabrapdf.net/?p=181

[TJL429]

They are saved with "PDF Compatabiliy." Acrobat is able to open the files individually but will not allow me to combine them into a pdf.