Additional files need to be installed to create PDF from this file (Excel). You must have Administrator Privileges to install these files

Old Issue but fix is to run Quick Repair on the Office installation 

Are you using the Portable version?
If so, you'll need to use an installable version because Adobe needs to access other applications (i.e ms word when combining .docx files to a pdf file).

In portable versions, permission is usually denied by Windows.

I had this problem as well and I found a solution!

The problem actually lies in Microsoft Office, not Adobe. You need to run a repair tool for Microsoft Office.  This tool is already installed on your computer if you have Office. Here is the solution:

Go to: Settings > Apps > Click "Microsoft 365 Apps for enterprise - en - us" > Modify > Allow changes > Quick Repair

Hope this helps!

Don't know if this will be of any help to anybody, but I had a device that was throwing up this error only when trying to combine or convert .docx files. I found in the Registry that the (Default) value under the regkey HKEY_CLASSES_ROOT\.docx was set incorrectly. I changed this to Word.Document.12 (I'm not sure if this will vary depending on the version of Office installed) and Acrobat was able to successfully work with .docx files again.

Looks like the device had been upgraded at some point from Windows 7 to 10 and Office 2010 to 2016, so I'm guessing the reg value at some stage of the process.

Hopefully this post will be of use to somebody out there.

I spoke with Adobe support in June 2020 and it's still an unresolved known issue.  Are they actively working on the issue or hoping it will just go away?  Four years seems like a long time to be working to resolve something.

This issue appears to continue to exist (Continuous Release version 2019.012.20035). Seeing as there was supposed to be a release to fix this back in 2016 (based on the dates on the posts here), I guess everyone just gave up, or maybe some miracle happened that fixed everyone and no one mentioned it here.

I have been as far on the web as I can get with Google's help trying to fix this problem, including messing around with DCOM permissions. Does anyone have an actual fix for this, or is it just a failure I'm going to have to learn to live with?

An update on my end - we also suffered from this problem. However, the root cause ended up being a too-strict security policy getting pushed out from our security team. When they rolled it back, Acrobat worked again.

Check your system events viewer.

Sorry wrong thread indeed. No idea how it happened! I wonder if I can find the message it belongs to... Sorry for the inconvenience

Yes a backup of the file. The file has corrupted, you need to go back to a version made before the damage. According to what I read.

Thank you for letting us know. It could help others with the same problem. It's surprising that nobody else has found it.